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MEDICAL APPLIED ANATOMY 



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MEDICAL 
APPLIED ANATOMY 

FOR STUDENTS AND PRACTITIONERS 



BY 



T. B. JOHNSTON, M.B., Ch.B. 

LECTURER ON ANATOMY, UNIVERSITY COLLEGE, LONDON 

LATELY LECTURER ON ANATOMY, EDINBURGH UNIVERSITY 

AND LECTURER ON MEDICAL APPLIED ANATOMY 

EDINBURGH POST-GRADUATE COURSES IN MEDICINE AND SURGERY 



CONTAINING THREE I'ULL-PAGE PLATES IN COLOUR 
AND I46 OTHER ILLUSTRATIONS IN THE TEXT 



LONDON 
A. AND C. BLACK LIMITED 

1915 



PREFACE 

For the last four years it has been my privilege to conduct a 
short course of lectures on Medical Applied Anatomy in 
connexion with the Edinburgh Post-Graduate Courses in 
Medicine and Surgery. At the suggestion of Dr. J. D. 
Comrie, the Medical Editor of the Edinburgh Medical Series, 
these lectures have been collected and expanded and are now 
issued in book form. 

As the realms of Medicine and Surgery are not sharply 
separated from one another, it has been a matter of some 
difficulty to avoid encroaching on the domain of Surgical 
Applied Anatomy, but the endeavour has been made to restrict 
the subject-matter so as to present, at moderate length, the 
more important applications of Anatomy to the study of 
Clinical Medicine. On this account, the subject has been 
treated according to Systems and not according to Regions, 
and it is hoped that the grouping of muscles with their nerves 
of supply under the Nervous System will be found useful by 
the reader. 

In collecting the material for this book, I have necessarily 
been indebted to the published works of numerous authors, 
and, more particularly, I wish to express my great indebted- 
ness to the writings of Mackenzie, Sahli, and Purves Stewart. 

For numerous suggestions and much helpful advice, 
always freely and willingly given, I owe my warmest thanks 
to Dr. J. D. Comrie. In addition, I gratefully acknowledge the 
help given me by Dr. A. Murray Drennan, who assisted in the 
laborious task of proof-reading, and by Dr. E. B. Jamieson, 
whose criticisms have always been of the greatest value. 

Some of the illustrations have appeared previously in other 
works. Figures 7, 8, 12, 15, 32, 33, 35, 36, 38, 39, 44, 49. 
51, 53, 55, 58, 79, 82, 114, and 115 are taken from Hirschfcld 



vi PREFACE 

and Leveille^s Atlas of Neurology. Their accuracy and 
artistic finish render no apology necessary for their reproduc- 
tion in this book. The tracings reproduced in Figures 107, 
in, and 112 were obtained for me by Dr. G. D. Mathewson, 
to whom I am greatly indebted. I wish to express my 
appreciation of the kindness of Dr. Knox, who helped to 
select and permitted me to reproduce three 'illustrations from 
his work on Radiography. I have also to thank Dr. S. G. 
Scott and Mr. Chas. A. Clark, who most kindly provided me 
with the radiographs ' which appear as Figures 142 and 84, 
respectively. 

At the present time anatomical nomenclature, so far as 
anatomical teaching is concerned, is unfortunately in a very 
chaotic condition. Until some general agreement can be 
come to with regard to this matter, not only by Anatomists, 
but also by all who are interested in the study and teaching 
of the Medical Sciences, no nomenclature can be regarded as 
completely satisfactory. In this book the Bale terminology, 
which has now been adopted in several medical schools in 
this country, has been used to a large extent, but the old and 
better known names have been inserted in brackets, wherever 
the possibility of confusion has arisen. The terms medial and 
lateral, however, have been used throughout in place of 
internal and external, and it has been considered unnecessary 
to insert the latter terms in brackets. It is hoped that the 
Glossary may be useful to those teachers of Clinical Medicine 
who desire to familiarise themselves with the Bale terminology. 
It must, however, be clearly understood that the Glossary 
contains only those terms which are commonly used in 
Clinical Medicine and which are not identical in the two 
terminologies. 

In conclusion, I hope that the book may prove of service 
and of interest, not only to the general practitioner, but also 
to the medical student during his study of Clinical Medicine. 

London, December 1914. 



CONTENTS 



' PAGE 

The Nervous System ..... i 

Development— The Neurone— The Brain— The Brain-Stem 
—The Motor Path— The Spinal Medulla— The Cerebral 
Nerves— The Membranes of the Brain— The Spinal Nerves 
—The Brachial Plexus— The Intercostal Nerves— The 
Lumbar Plexus— The Sacral Plexus— The Sympathetic 
Nervous System — Referred Pain. 

II 

The Organs of Special Sense . . .198 

The Ear— The Eye— The Nose. 

Ill 

The Digestive System . . • .219 

The Teeth — The Salivary Glands — The Mouth — The 
Pharynx — The (Esophagus — The Peritoneum — The 
Stomach— The Small Intestine— The Liver and Bile Ducts 
— The Pancreas — The Portal Circulation — The Large 
Intestine — Developmental Anomalies. 

IV 

The Vascular System . . . .288 

The Pericardium— The Heart— The Ecetal Circulation- 
Congenital Anomalies— Cardiac Pain— The Heart Muscula- 
ture—The Venous Pulse— The Heart Rhythm— The Great 
Vessels. 



viii CONTENTS 

V 

PAGE 

The Respiratory System .... 325 

The Nose — The Naso-Pharynx — The Larynx — The Trachea 
and Bronchi — The Pleural Sacs — The Lungs. 

VI 
The Genito-Urinary System . . . -357 

The Kidneys — The Ureter— The Bladder — Congenital Anom- 
alies — The Prostate — The Testis- — The Urethra — The 
Female Pelvis and Reproductive Organs. 

VII 
The Ductless Glands .... 400 

The Hypophysis — The Spleen — The Supra-renal Glands — 
The Thyreoid Gland — The Thymus. 

Glossary . . . . -415 



Index . 



423 



LIST OF ILLUSTRATIONS 



COLOURED TLATES 

PLATE 

I. The Postero-inferior Aspect of the Liver . .facing p. 260 

II. General View of the Abdominal and Thoracic Viscera"} between pp. 344 
III. The Abdominal and Thoracic Viscera from behind ) and 345 



IN THE TEXT 

fig. r-«E 

1. Transverse Section of Human Embryo . . . . 1 

2. Section through cephalad extremity of Neural Tube . . 2 

3. Lateral Aspect of Left Cerebral Hemisphere . . .6 

4. Lateral Aspect of Skull, showing the relations of important 

structures to the surface ..... 7 

5. Median Sagittal Section through the Brain-Stem, showing the 

third and fourth ventricles and their connexions . .11 

6. Medial Aspect of Right Cerebral Hemisphere . . 13 

7. The Tela Chorioidea (velum interpositum) viewed from above . 14 

8. The Inferior Aspect of the Brain . . . . 17 

9. Medial Aspect of Right Cerebral Hemisphere . . .18 

10. Transverse Section through the Mid-Brain . . 19 

11. The Lateral Aspect of the Brain-Stem . . . 19 

12. The Anterior Aspect of the Brain-Stem . . . .20 

13. Dissection to show the Floor of the Lateral Ventricle. (Turner's 

Anatomy.) . . . . . . .24 

14. Median Sagittal Section through the Brain-Stem, showing the 

third and fourth ventricles and their connexions . . 25 

15. The Tela Chorioidea (velum interpositum) viewed from above . 26 

16. Lateral Aspect of Skull, showing the relations of important 

structures to the surface . . . . .28 

17. The Lateral Aspect of the Brain-Stem . . . .29 

18. Horizontal Section through Left Cerebral Hemisphere . 31 



LIST OF ILLUSTRATIONS 



FIG. PAGE 

19. Frontal (Coronal) Section through Left Cerebral Hemisphere . 32 

20. Diagram to illustrate Innervation of a Muscle by both Cerebral 

Hemispheres . . . . . . -34 

21. Dissection of Brain, showing the Lateral Aspect of the Internal 

Capsule . . . . . . 36 

22. Diagram of Frontal (Coronal) Section of Right Cerebral Hemi- 

sphere and Brain-Stem, showing the path of the Motor Fibres 38 

2^. Transverse Section through the Pons (Diagrammatic) . . 40 

24. Foetal Skull, seen from above. (Johnstone's Midwifery. ) . 42 

25. Transverse Section through Spinal Medulla (Schematic) . . 44 

26. Diagram to illustrate the course taken by Sensory Fibres after 

entering the Spinal Medulla . . . . -45 

27. Floor of Skull ....... 49 

28. Diagram of course of Visual and Pupillary Fibres . . 5° 

29. The Lateral Aspect of the Brain-Stem . . . • 5 1 

30. Dissection of Brain, showing the Lateral Aspect of the Internal 

Capsule ....... 53 

31. Transverse Section through the Cavernous Sinus . . 55 

32. The Posterior Aspect of the Brain-Stem . . . .56 

33. The Muscles of the Orbit . . . . -59 

34. Transverse Section through the Pons (Diagrammatic) . . 62 

35. Interior of the Skull after the removal of the Brain, showing the 

points of exit of the twelve cerebral nerves . . -63 

36. The Branches of the Ophthalmic Nerve . . . .64 

37. The Cutaneous Branches of the Trigeminal Nerve . . 66 

38. The Branches of the Maxillary Nerve . . . -67 

39. The Branches of the Mandibular Nerve . . . • 7 1 

40. The Cutaneous Branches of the Trigeminal Nerve . . 74 

41. The Areas of Skin supplied by the three divisions ol the 

Trigeminal Nerve . . . . . -76 

42. Transverse Section through the Pons (Diagrammatic) . . 79 

43. Schematic representation of the Branches of the Facial Nerve . 81 

44. The Facial Nerve and its Ramifications . . . -83 

45. Schematic representation of the course of the Taste Fibres . 85 

46. Diagram to show the path of the Fibres of the Cochlear Nerve . 88 

47. Section through Upper Part of Medulla Oblongata . . 91 

48. The Lateral Aspects of the Larynx and Pharynx, showing their 

Nerves of Supply . .... 93 

49. The Course, Relations and Branches of the Left Vagus Nerve . 95 

50. Transverse Section through the Neck at the level of the First 

Thoracic Vertebra . . . . . .98 

51. Interior of the Skull after the removal of the Brain, showing the 

points of exit of the twelve cerebral nerves . . . 102 



LIST OF ILLUSTRATIONS xi 

FIG. PAGE 

52. Section through Upper Part of Medulla Oblongata . .105 

53. The Cranial Blood Sinuses . . . . .110 

54. Median Sagittal Section through the Brain-Stem, showing the 

third and fourth ventricles and their connexions . .112 

55. The Cranial Blood Sinuses . . . . • "3 

56. Transverse Section through the Cavernous Sinus . . 1 1 5 

57. Lateral Aspect of Skull, showing the relations of important 

structures to the surface . . . . . 1 1 7 

58. Interior of the Skull after the removal of the Brain, showing the 

points of exit of the twelve cerebral nerves . . .118 

59. Diagram to illustrate the course taken by Sensory Fibres after 

entering the Spinal Medulla . . . . .123 

60. The Areas of Skin supplied by the Posterior Rami (primary 

divisions) of the Spinal Nerves .... 125 

61. The Nerve-supply of the Anterior Aspect of the Trunk . 127 

62. Diagram to show the branches and the mode of formation 

of the Cervical and the Brachial Plexuses. (Turner's 
Anatomy.) . ■ ■ • • • -13° 

63. The Nerve-supply of the Skin on the Anterior Aspect of the 

Upper Limb . . . • • • • ! 35 

64. The Nerve-supply of the Skin on the Dorsal Aspect of the 

Upper Limb . . . • • • T 39 

65. The Nerve-supply of the Skin on the Anterior Aspect of the 

Upper Limb . . • • • • 143 

66. Tendons attached to a Finger. (Turner's Anatomy.) . . 146 

67. The Nerve-supply of the Skin on the Dorsal Aspect of the 

Upper Limb . . . . • • 1 53 

68. Diagram representing the development of the Upper Limb, and 

the segmental arrangement of its Sensory Nerve-supply . 158 

69. The Nerve-supply of the Anterior Aspect of the Trunk . . 161 

70. The Lumbar, Sacral and Pudendal Plexuses. (Turner's Anatomy. ) 164 

71. The Nerve-supply of the Skin on the Anterior Aspect of the 

Lower Limb ...... 168 

72. The Lumbar, Sacral and Pudendal Plexuses. (Turner's 

Anatomy.) . . ■ ■ • • I7 1 

73. The Nerve-supply of the Skin on the Anterior Aspect of the 

Lower Limb . . . • • • .179 

74. The Nerve-supply of the Skin on the Posterior Aspect of the 

Lower Limb . . . • • • .181 

75. Diagram of the Sympathetic Nervous System . . .186 

76. Diagram to explain a Viscero-sensory Reflex . . . 191 

77. Section through the Auricle, the External Acoustic Meatus 

and the Tympanum. (Turner's Anatomy.) . . 201 



xii LIST OF ILLUSTRATIONS 

FIG. PAGE 

78. Lateral Aspect of Right Tympanic Membrane . . . 203 

79- The Facial Nerve traversing the Facial Canal in the Petrous 

Part of the Temporal Bone ..... 204 

80. Diagram of the Membranous Labyrinth. (Turner's Anatomy. ) 207 

81. The Lacrimal Apparatus. (Turner's Anatomy.) . . 209 

82. Antero-Posterior Median Section through the Eyeball . 213 

83. The Normal Fundus, showing the Porus Opticus (Optic Disc) 

and the Retinal Blood-vessels . . . .217 

84. Radiogram of Anterior Portion of Head, showing non-eruption 

of the third upper molar tooth of the right side. (From a 
Radiography by Chas. A. Clark, Esq., L.D.S.Eng. ) . 221 

85. The Parotid Gland and its Duct .... 223 

86. The Interior of the Pharynx, viewed from behind . . 227 

87. Anterior Aspect of Trunk, showing the planes utilised for the 

surface topography of the abdominal viscei a . . 233 

88. Median Sagittal Section through the Abdomen, to show the 

arrangement of the Peritoneum. (Turner's Anatomy.) . 235 

89. Diagram of the Stomach and the Lesser Omentum . . 236 

90. Transverse Section through the Abdomen at the level of the 

epiploic foramen (of Winslow), to show the disposition of 

the Peritoneum ...... 238 

91. Transverse Section through the Abdomen, below the level of the 

epiploic foramen (of Winslow) .... 239 

92. Anterior Aspect of the Trunk, showing the surface relations of 

the liver, the stomach and the large intestine . . 244 

93. The relations of the Left Kidney and the Viscera which form the 

" bed" of the Stomach ..... 245 

94. Normal Tonic Stomach. (From Knox's /vWw^-a^j.) . 246 

95. Atonic, dilated, Stomach. (From Knox's Radiography. ) . 247 

96. The Nerve-supply of the Anterior Aspect of the Trunk . 251 

97. The relations of the Right Kidney, the Duodenum and the Head 

of the Pancreas ...... 254 

98. Diagram of the Bile Duct and the Pancreatic Ducts, showing 

how they open into the Duodenum .... 263 

99. The relations of the Right Kidney, the Duodenum and the Head 

of the Pancreas ...... 267 

100. The Portal Vein and its Tributaries. (Turner's Anatomy.) . 273 

101. Anterior Aspect of the Trunk, showing the surface relations of 

the liver, the stomach and the large intestine . . 277 

102. The Rectal Valves ...... 282 

103. The Development of the Bladder and Rectum . . . 286 

104. Diagram of a Sagittal Section through the Heart and the 

Pericardium ....... 289 



LIST OF ILLUSTRATIONS xiii 

FIG. PAGE 

105. Diagram of a Transverse Section through the upper part of the 

Pericardium ....... 290 

106. Anterior Aspect of the Chest, showing the surface relations of 

the heart and great vessels, the lungs and the pleural sacs . 295 

107. Sphygmographic Tracing of a Normal Pulse . . . 301 

108. Diagram to show the positions of the valves on the tributaries 

of the Superior Vena Cava ..... 302 

109. Diagram of the primitive tubular Heart of the Embryo . 303 
no. Diagram to illustrate the Fcetal Circulation . . . 305 
in. Tracing of the Normal Venous Pulse, together with a 

synchronous tracing of the Radial Pulse . . • 3 11 

112. Tracings from a case of Complete Heart-block . . . 313 

113. Transverse Section through the Thorax at the level of the 

fourth thoracic vertebra ..... 3 20 

114. The Nasal Septum ....•• 3 2 ^ 

115. Frontal (Coronal) Section through the Skull, showing the nasal 

fossae ....... 3 2 ^ 

116. Posterior Aspect of the Cartilages of the Larynx. (Turner's 

Anatomy.) . . ■ ■ • • • 33 1 

117. The Interior of the Pharynx viewed from behind . . 333 
11S. Frontal (Coronal) Section through the Larynx. (Turner's 

Anatomy.) ....••• 334 

119. The Interior of the Left Half of the Larynx. (Turner's 

Anatomy.) . . . . . • • 33^ 

120. Tranverse Section through the Larynx at the level of the vocal 

folds (true vocal cords). (Turner's Anatomy.) . . 337 

121. The Larynx, Trachea and Bronchi .... 340 

122. Diagram of a Transverse Section through the Thorax above 

the level of the root of the lung, showing the arrangement 

of the parietal and visceral layers of the pleura . . 342 

123. Diagram of a Transverse Section through the Thorax at the 

level of the root of the lung. The continuity of the visceral 

and the parietal layers is demonstrated in the figure . 343 

124. Anterior Aspect of the Trunk, showing the surface relations of 

the kidneys and ureters, the duodenum and the pancreas . 358 

125. The relations of the Left Kidney and the Viscera which form 

the " bed " of the Stomach . . . . -359 

126. The Spleen and the Left Kidney and Ureter outlined on the 

Dorsal Aspect of the Body . . . . . 362 

127. Median Sagittal Section of Male Pelvis, showing the relations 

of the viscera and the arrangement of the peritoneum . 366 

128. Median Sagittal Section through Male Pelvis, showing the 

disposition of the peritoneum when the bladder is distended 368 



xiv LIST OF ILLUSTRATIONS 



PAGE 



FIG. 

129. The Development of the Bladder .... 370 

130. The Nerve-supply of the Anterior Aspect of the Trunk . . 372 

131. Diagram of the Male Reproductive Organs. (Turner's Anatomy.) 376 

132. The Urinary Bladder and the Prostate, viewed from behind . 378 

133. The Development of the Male Reproductive Organs . . 381 

134. Median Sagittal Section through the Female Pelvis, showing 

the relations of the viscera and the arrangement of the 
peritoneum . . . • • • 3$4 

135. Diagram of a Sagittal Section through the Broad Ligament of 

the Uterus and its contents ..... 385 

136. Diagram of a Transverse Section through the Uterus and the 

Broad Ligaments, near the lower borders of the latter, 
showing the relation of the uterine artery to the ureter . 386 

137. The Uterus and the Broad Ligaments, viewed from in front. 

(Turner's Anatomy.) . . . . -39° 

138. Diagram of a Transverse Section through the Uterus and the 

Broad Ligaments, near the lower borders of the latter, 
showing the relation of the uterine artery to the ureter . 392 

139. The Broad Ligaments of the Uterus, viewed from behind. 

(Turner's Anatomy.) ..... 394 

140. Diagram of the Development of the Female Generative Organs 397 

141. Radiogram of Skull, showing a normal hypophyseal (pituitary) 

fossa. (From Knox's Radiography.) . . .401 

142. A much enlarged Hypophyseal Fossa, caused by a tumour of* 

the Hypophysis (pituitary body). (From a Radiograph taken 

by Dr. S. G. Scott.) . . . .402 

143. The Spleen and the Left Kidney and Ureter outlined on the 

Dorsal Aspect of the Body ..... 403 

144. Transverse Section through the Abdomen at the level of the 

epiploic foramen (of Winslow), to show the disposition of 

the peritoneum ...... 4°5 

145. The relations of the Left Kidney and the Viscera which form 

the " bed " of the Stomach . . . . . 4°7 

146. Transverse Section through the Neck at the level of the First 

Thoracic Vertebra . . . . . .410 



MEDICAL APPLIED ANATOMY 



I 
THE NERVOUS SYSTEM 

Development of the Nervous System. — Before the different 
parts of the nervous system are described, it is necessary to 
outline, as briefly as possible, the developmental history of 
the nervous system as a whole. 

During the first week of intra-uterine life, a longitudinal 




Fig. i. — Transverse Section of Human Embryo. 

A. Ectoderm. C. Endoderm. E Vitello-intestinal duct. 

B. Neural groove. D. Mid-gut. I F. Yolk-sac. 

groove, which rapidly increases in depth, appears in the 
ectoderm on the dorsal surface of the human embryo (Fig. i). 
At a slightly later stage, the edges of the groove coalesce so 
as to form a tube, which soon loses its connexion with the 
surface ectoderm. This tube is lined entirely by ectoderm 
i 



2 THE NERVOUS SYSTEM 

and it subsequently gives rise to the whole of the nervous 
system. 

From the lateral walls of the cephalic (or anterior) extremity 
of the neural tube, which persists in the adult as the third 
ventricle, two diverticula grow out, one on each side, and form 
the cerebral hemispheres. The cavities of the diverticula persist 
as the lateral ventricles and their connexions with the primi- 
tive tube remain in the adult as the interventricular foramina 
(of Monro) (Fig. 2). 

The fourth ventricle arises as a dilatation of the neural 
tube, caudal to the lateral diverticula, and the part of the tube 
immediately cephalad to this dilatation subsequently forms 



Cr3, 



Fig. 2. — Section through cephalad extremity of Neural Tube. 

A. Neural tube. B. Primitive interventricular foramen (of Monro). 

C. Developing lateral ventricle. 

the cerebral aqueduct (of Sylvius), which connects the fourth 
ventricle with the third ventricle in the adult (p. 15). The 
caudal (or posterior) portion of the tube persists as the central 
canal of the spinal medulla (spinal cord). 

The ectodermal cells which line the neural tube undergo 
specialisation. Some of them are converted into nerve-cells ; 
others form the neuroglia, which constitutes the supporting 
tissue of the nervous system ; while others form the ependyma, 
which lines the whole of the interior of the ventricular system. 
Over the caudal part of the roof of the fourth ventricle the 
ectoderm gives rise only to ependyma, so that in this situation 
the ependyma comes into direct contact with the overlying 
pia mater (p. in). 



THE NEURONE 3 

The Neurone. — Each nerve-cell consists of a body, variously 
shaped and containing a nucleus, a nucleolus, etc., and certain 
processes. The processes are of two kinds — (a) the dendrites, 
which are usually short and break up into numerous branches, 
and (l>) the axon or axis cylinder, which varies in length and 
gives off no branches of note prior to its termination. 

Physiologically, so far as we know at present, the axon is 
of much greater importance than the dendrites, and impulses 
arising within the cell, or destined for it, are transmitted along 
the axon. 

The term "Neurone" includes the nerve-cell and all its 
processes. Neurones can be divided, broadly, into two 
groups : — (a) Those engaged in carrying impulses from the 
cerebral cortex to the periphery, efferent neurones ; and (b) 
those engaged in carrying impulses from the periphery to the 
cerebral cortex, afferent neurones. 

Efferent stimuli arising in the cortex traverse two or more 
neurones before they reach their destination, and these 
neurones must all be physiologically intact before the stimulus 
can produce its result. The uppermost neurone has its cell 
situated in the cerebral cortex and the lowermost neurone 
has its cell in the grey matter of the brain stem or the spinal 
medulla (spinal cord). In the case of the voluntary muscles, 
interruption of the upper neurone prevents the stimulus from 
passing on to its destination and the muscle involved is 
paralysed, i.e. it is unable to react to cerebral stimuli, 
although its electrical reactions are not altered. As the 
lower neurone is not damaged, the trophic influence which 
the nerve-cells exert on the tissues they supply is not interfered 
with and the muscle involved will suffer atrophy from disuse 
only. In addition to originating voluntary stimuli, the upper 
neurone exerts a subconscious controlling action on the lower 
neurone and, when this controlling action is removed, the 
muscle, typically, assumes a spastic contraction. On the 
other hand, when the lower neurones are interrupted, their 
axons are cut off from the cell body and undergo degeneration. 



4 THE NERVOUS SYSTEM 

As a result, the muscle involved is not only paralysed but its 
electrical reactions become altered. Further, the trophic 
influence of the lower neurone being removed, the muscle 
atrophies. At the same time, the controlling "tonic" influence 
is cut off and the muscle, losing its tonus, becomes flaccid. 

Afferent stimuli have their origin in the periphery, often in 
special nerve-endings, and they pass along the axons to the 
spinal medulla. Either in the spinal medulla or in the brain 
stem the axons end by arborising round nerve-cells and the 
impulses which they convey are transferred to these upper 
neurones. After passing through one, two or more relays, the 
afferent impulse eventually reaches the cortex and, depending 
on its nature, is interpreted or causes a reacting efferent 
impulse. 

Under normal conditions, an afferent impulse stimulates only 
a group of axons and the neurones to which they belong, and 
then is transmitted to the cerebral cortex ; but, under abnormal 
conditions, an afferent impulse may spread from the cells for 
which it was primarily intended and affect the neighbouring 
nerve-cells. Of the nature of this " overflow " we know as 
little as we do about the nature of the original impulse, but, 
apparently, stimulation of a neurone by " overflow " from 
adjoining neurones produces precisely the same results as 
stimulation arising at its peripheral part. In this way, impulses 
ascending along the phrenic nerve (C, 3, 4 and 5) reach nerve- 
cells in the fourth cervical segment, and, when these impulses 
are altered, as in diaphragmatic pleurisy, they may overflow 
and stimulate the adjoining cells, which normally receive 
peripheral stimuli only from the skin of the neck and shoulder. 
Such an overflow therefore causes stimuli to reach nerve-cells 
in the cortex, and these cells interpret all stimuli as pain in the 
region of the neck and shoulder. Pain of this nature is termed 
"referred pain." The condition is described more fully in 
connection with Mackenzie's " Visceio-Sensory " and " Viscero- 
motor Reflexes " on page 190. 



THE CEREBRUM 



THE BRAIN 



The Parts of the Central Nervous System. — The Brain is 
divided into two symmetrical hemispheres by the great longi- 
tudinal fissure, but the two halves are connected to one 
another by commissural bands, of which the corpus callosum 
(p. 10) is the most important. The mid-brain descends from 
the middle of the basal surface of the brain and is continuous 
below with the pons, which in turn becomes continuous with 
the medulla oblongata. These three structures form the 
brain-stem and, together with the cerebellum, which projects 
backwards behind them, they occupy the posterior cranial 
fossa. At the foramen magnum in the occipital bone the 
medulla oblongata becomes continuous with the spinal medulla 
(spinal cord). 

The Lateral Surface of the Brain 

The Central Sulcus (of Rolando) is the most important 
sulcus on the lateral surface of the cerebral hemisphere. It 
is directed obliquely downwards and forwards and is situated 
between two parallel and nearly vertical convolutions, which 
are termed the anterior and the posterior central gyri. In- 
feriorly, the central sulcus terminates a little above the 
posterior ramus of the lateral fissure (of Sylvius) (Fig. 3). 

The grey matter of the anterior central gyrus and of the 
anterior wall of the central sulcus contains the higher motor 
centres. The centre for the muscles of the lower limb is situ- 
ated in the uppermost part of the anterior central gyrus, and 
it extends over the supero-medial border of the hemisphere 
for a short distance on to the medial surface (Fig. 6). 
Immediately below the centre for the lower limb, and 
slightly overlapping it, lies the centre for the muscles of the 
trunk, while the upper limb centre is placed a little lower and 
occupies that part of the anterior central gyrus which pro- 
jects backwards following the curve of the central sulcus 



6 THE NERVOUS SYSTEM 

(Fig. 3). The lowest part of the anterior central gyrus con- 
tains the motor centres for the face, head and neck. 

Before the axons from the nerve-cells of the motor area of 
the cortex reach their destination, they all, with certain 
exceptions to be noted later (pp. 34 and S6), cross the 
median plane. Cortical lesions in this situation, therefore, 
produce their effects on the opposite side of the body and, 



z 3 




Fig. 3. — Lateral Aspect of Left Cerebral Hemisphere. 

7. Post-central sulcus. 

8. Supra-marginal gyrus. 

9. Post-parietal gyrus. 

10. 1 

\, Rami of lateral 

I fissure (of Sylvius). 



1. Inferior frontal sulcus. 

2. Superior frontal sulcus. 

3. Inferior precentral sulcus. 

4. Superior precentral sulcus. 

5. Central sulcus (of Rolando). 

6. Posterior central gyrus. 



T3. Superior temporal sulcus. 



owing to the extent of the anterior central gyrus, they are not 
likely to involve the whole of the motor area. The effects 
of the lesion may be irritative or paralytic, according to its 
nature, or the second condition may ensue after a temporary 
irritative stage. Irritative conditions of the motor cortex do 
not necessarily depend on the existence of an organic lesion, 
and in many cases of epilepsy no such lesion is present. 



THE CEREBRUM 



Organic lesions, sooner or later, lead to paralysis, which is 
usually distributed over two regions, whose centres overlap 
one another in the anterior central gyrus. A pure mono- 
plegia of cortical origin is extremely rare and, when it does 




Fig. 4. — Lateral Aspect of Skull, showing the relations. of important 
structures to the surface. 



1. Zygomatic arch. 

2. Middle meningeal artery. 

3. Greater wing of sphenoid. 

4. Glabella. 

5. Temporal line. 

6. Anterior branch of middle meningeal 

artery. 

7. Central sulcus (of Rolando). 

8. Coronal suture. 

9. Lateral fissure, posterior ramus. 



10. Superior temporal sulcus, 
n. Posterior branch of middle meningeal 
artery. 

12. Line drawn from floor of orbit through 

centre of external acoustic meatus. 

13. External occipital protuberance. 

1 . Site for puncture of lateral ventricle. 

2 . Site for puncture of inferior horn of 

lateral ventricle. 



occur, it involves the lower limb. The condition is dia- 
gnostic of a lesion in the posterior part of the medial surface 
of the frontal lobe (Fig. 6). 

The upper extremity of the central sulcus corresponds on 
the surface of the skull to a point which lies half an inch 
behind the mid-point of the line joining the glabella (the 



8 THE NERVOUS SYSTEM 

elevation immediately above the root of the nose) to the 
external occipital protuberance; its lower extremity lies 2 inches 
vertically above the pre-auricular point, which is situated on 
the zygomatic process of the temporal bone immediately in 
front of the tragus of the external ear. The line joining these 
two points indicates, on the surface of the head, the position 
and direction of the central sulcus, and the-area which extends 
for three-quarters of an inch anterior to it overlies the anterior 
central gyrus. Firm pressure or percussion over this area may 
produce pain in organic lesions of the motor cortex. 

The Middle Frontal Gyrus lies anterior to the middle third 
of the anterior central gyrus, from which it is separated by 
the precentral sulci (Fig. 3). It is said to contain the motor 
centres for the muscles of the eye. Turner and Ferrier 
removed this portion of the cortex in monkeys, but, although 
the operation produced temporary conjugate deviation of the 
head and eyes towards the side of the lesion, the condition 
was rapidly recovered from, and the animal regained free 
control over all the muscles of the eye and the head and neck. 
Irritative lesions in this region may give rise to deviation of 
the head and eyes to the opposite side, but the great majority 
of such lesions give rise to no localising motor symptoms 
unless they extend backwards and involve the anterior central 
gyrus. 

Lesions of the frontal lobe, anterior to the precentral sulcus, 
may give rise to mental symptoms, but these vary so much 
that they are not of great help in topical diagnosis. Failure 
of memory, alterations in personal disposition, loss of concen- 
trative powers, are features which have been noted in some 
cases. 

The posterior part of the middle frontal gyrus is said to 
contain the higher centres for written speech. In cortical 
lesions of this area the patient is unable to write intelligible 
sentences or words, although he can read and speak quite 
intelligently and understands what is said to him. 

The Lateral Fissure (of Sylvius) begins on the basal 



THE CEREBRUM 9 

surface of the brain at the lateral side of the anterior per- 
forated substance (ant. per/, spot) (p. 16) and passes laterally, 
separating the temporal from the frontal lobe. When it 
reaches the lateral surface of the brain, it divides into three 
rami. The anterior horizontal and the anterior ascending 
rami pass forwards and upwards, respectively, into the inferior 
frontal gyrus, and the cortical areas which surround them 
constitute the area of Broca. The motor speech centre is 
situated in this area, on the left side of the brain in right- 
handed subjects and on the right side of the brain in left- 
handed subjects. Cortical lesions of Broca's area cause 
motor aphasia, but, if the lesion is localised, the patient can 
understand what is said to him and can read and write 
intelligently. 

The posterior ramus of the lateral fissure runs backwards, 
separating the frontal and parietal lobes above from the 
temporal lobe below, and finally it turns upwards to end in the 
parietal lobe. At its termination it is surrounded by the 
supramarginal gyrus, which lies under cover of the parietal 
tuber {eminence') (Fig. 4). 

The Superior Temporal Sulcus lies in the temporal lobe below 
and parallel to the posterior ramus of the lateral fissure, and it 
also turns upwards to end in the parietal lobe. Its extremity 
is surrounded by the angular gyrus, which contains the visual 
speech centre. In cortical lesions of this gyrus, the patient 
cannot understand written or printed matter, although other- 
wise his vision may be quite unaffected and he can speak and 
write intelligibly. The latter action may be carried out with 
difficulty, as he cannot appreciate whether he is writing sense 
or nonsense. 

The Superior Temporal Gyrus lies between the posterior 
ramus of the lateral fissure above and the superior temporal 
sulcus below. It contains the higher auditory and word- 
hearing centres and, when involved in pathological conditions, 
it gives rise to partial deafness of the opposite ear (p. 89). 

The Superior Parietal Gyrus is a strip of cortex which is 



io THE NERVOUS SYSTEM 

situated between the supero-medial border of the hemisphere 
and the angular and supramarginal gyri. From the two 
latter it is separated by the ramus horizontalis of the post- 
central sulcus. It is believed to contain the centre for stereo- 
gnosis, the sense by which objects can be identified by tactile 
impressions only. When symptoms of cerebral tumour are 
present, the development of astereognosis. indicates that the 
tumour is situated in the neighbourhood of the superior 
parietal gyrus. Cases of astereognosis have also been 
recorded in which the lesion has been confined to the supra- 
marginal convolution (Fig. 3). 

The posterior part of the lateral surface of the cerebrum 
belongs to the occipital lobe. This portion of the cortex 
contains some of the higher visual centres, but as they appear 
to be connected more intimately with the medial surface of the 
occipital lobe, their description is deferred until that aspect 
of the brain is described (p. 12). 

When the lips of the posterior ramus of the lateral fissure 
are drawn apart, a submerged area, of the cerebral cortex is 
brought into view. This area is termed the Island (of Reil). 
It is of value as a landmark in the study of sections of the 
brain which pass through the anterior part of the cerebral 
hemisphere (Fig. 18). Practically nothing is known about its 
functions, and, although Campbell has suggested that its 
anterior portion contains the higher centres for the sense of 
taste, his views have no clinical evidence to support them. 

The Medial Surface of the Cerebral Hemisphere 

The most noticeable structure on the medial surface is the 
Corpus Callosum. It consists of white matter, the fibres of 
which run mainly in a transverse direction and connect cortical 
areas of one hemisphere to the corresponding areas of the 
other. The posterior extremity of the corpus callosum, which 
is termed the splenium, forms a rounded swelling, overhanging 
the posterior aspect of the mid-brain (Fig. 5). The body 



THE CEREBRUM 



1 1 



of the corpus callosum extends forwards from the splenium 
to the genu, where it bends sharply downwards and backwards 
to end in a pointed extremity, which is termed the rostrum. 

Cases of maldevelopment or congenital absence of the 
corpus callosum have been recorded, but, although some 

Septum pelluuidum 
Corpus callo-um \ [r ; 

V I 



Interventricular foramen--"" 
Lamina terminalis — 



Oculo-motor nerve 



-— Middle commissure 



_ — Pineal body 
_ _ - Corpora quadrigemina 

^ Cerebral aqueduct 
(of Sylvius). 

Fourth 

"" ventricle 




•*r — _ _ Central canal of 
\ spinal medulla 



Fig. 5. — Median Sagittal Section through the Brain-Stem, showing the 
third and fourth ventricles and their connexions. 



were associated with mental dulness, others appear to have 
produced no symptoms during life and were only discovered 
accidentally in the post-mortem or dissecting room. Four 
cases of tumour involving the corpus callosum, three of which 
were primary, have been described by Btistowe, who believes 
that it may be possible to recognise the condition during the 



12 THE NERVOUS SYSTEM 

life of the patient. The condition, like all cerebral tumours, 
is progressive; paral>tic symptoms appear gradually, and 
paralysis of one side of the body is associated with vague 
hemiplegic symptoms on the other ; a tendency to drowsiness 
and stupidity supervenes. At the same time, none of the 
cerebral nerves are directly involved, since none of them are 
in intimate relation with the corpus callosum. 

Very little is known with regard to the functions of the 
large cortical areas which lie above and in front of the corpus 
callosum. This part of the medial surface is divided into 
upper and lower areas by the sulcus cinguli {calloso-marginal 
fissiur), which ascends to the supero-medial border of the 
hemisphere a little in front of the splenium (Fig. 6). The 
upper area is termed the marginal gyrus and its posterior 
part is termed the paracentral lobule. The latter is usually 
cut into by the upper extremity of the central sulcus and it 
contains some of the higher motor centres for the lower limb 
of the opposite side (Fig. 6). 

The gyrus cinguli (callosal gyrus) lies between the sulcus 
cinguli and the corpus callosum. When it is traced backwards 
it curves downwards and forwards round the splenium and 
becomes continuous with the hippocampal gyrus on the basal 
surface of the cerebrum. These two gyri together constitute 
the gyrus fornicatus (limbic lobe). 

Experimental and clinical evidence suggests that some of 
the higher sensory centres are situated in the gyrus cinguli, and 
lesions in this situation usually produce some alterations in 
sensibility on the opposite side of the body. 

From the region of the occipital pole, the Calcarine Fissure 
passes forwards and meets the Parieto-Occipital Fissure at an 
acute angle below the splenium of the corpus callosum 
(Fig. 6). The area contained between these sulci and the 
supero-medial border of the hemisphere is known as the 
Cuneus. It belongs to the occipital lobe and contains some 
of the higher visual centres. A cortical lesion of the cuneus 
produces blindness in the lower lateral quadrant of the 



THE CEREBRUM 



13 



retina of the same side and in the lower medial quadrant of 
the retina of the opposite side. This condition is known as 
lower quadrantic hemianopia. If, however, the lesion is con- 
fined to the area below the calcarine fissure, the upper 




10 


y 


','A 


II 


12' 
13 


s 

14 


v 

16'' 

if 



Fig. 6.— Medial Aspect of Right Cerebral Hemisphere. 



1. Genu of corpus callosum. 

2. ( lyrus cinguli. 

3. Sulcus cinguli (calloso-marginal). 

4. Body of corpus callosum. 

5. Motor centre for lower limb. 

6. Central sulcus (of Rolando). 

7. Splenium of corpus callosum. 

8. Parieto-occipital fissure. 

9. Cuneus. 

10. Rostrum of corpus callosum. 

11. Septum pellucidum. 



12. Column of fornix. 

13. Interventricular foramen (of Monro). 

14. Thalamus. 

15. Lamina terminalis. 

16. Optic chiasma. 

17. Uncus. 

18. Cut surface of mid-brain. 

19. Calcarine fissure. 

20. Collateral fissure. 
2t. Lingual gyrus. 
22. Calcarine fissure. 



quadrants of the retina? are affected. Finally, when the 
lesion involves both areas, homonymous hemianopia is the 
result (see p. 52). 

The Septum Pellucidum is a bilaminar membrane which 
occupies the concavity of the genu of the corpus callosum 



H 



THE NERVOUS SYSTEM 



(Fig. 6), and serves to separate the anterior parts of the 
lateral ventricles from one another (Fig. 7). It is attached 
posteriorly to a flattened band of white fibres, termed the 
fornix, which, although separated in this way from the genu, 
is closely applied to the inferior surface of the body of the 




Fig. 7. — The Tela Chorioidea (velum interpositum) viewed from above. 



1. Tela chorioidea. 

2. Chorioid plexus. 

3. Thalamus. 

4. Caudate nucleus. 



5. Septum pellucidum (cut). 

6. Vein of corpus striatum. 

7. Stria terminalis. 

8. Great cerebral vein (of Galen). 
9. Internal cerebral vein. 



corpus callosum. The column {anterior pillar) of the fornix 
sinks into the substance of the medial surface of the brain as 
it descends to establish connexions with the corpus mamillare 
(p. 16). 

The Thalamus is a large mass of grey matter which lies 



THE CEREBRUM 15 

below the fornix. Its free, medial surface (Fig. 5) forms 
the lateral wall of the third ventricle and is covered by 
ependyma, which can be traced downwards and backwards 
to the cerebral aqueduct (of Sylvius). The anterior extremity 
of the thalamus is separated from the column (anterior pillar) 
of the fornix by the Interventricular Foramen (of Monro), 
through which the ependyma of the third ventricle passes 
to become continuous with the ependyma lining the lateral 
ventricle. 

A fold of pia mater, termed the tela chorioidea (velum inter- 
positum), is carried into the interior of the brain below the 
splenium of the corpus callosum. It is situated between the 
inferior aspect of the fornix and the superior aspects of the 
thalami, and extends as far forwards as the interventricular 
foramen. In the median plane, the thalami are separated 
from one another by the third ventricle, the roof of which is 
formed by the tela chorioidea as it crosses from one side to 
the other. The large veins which return the blood from the 
substance of the brain are situated between the two layers 
of the tela chorioidea, and they emerge at its posterior edge 
between the splenium above and the dorsal aspect of the 
mid-brain below (Fig. 7). 

In a median sagittal section of the brain, the mid-brain is 
divided immediately below the thalamus (Fig. 5). It is 
traversed, near its dorsal aspect, by the cerebral aqueduct 
(of Sylvius), which becomes greatly dilated behind the lower 
part of the pons and the upper part of the medulla oblongata, 
forming the fourth ventricle. 



The Basal Surface of the Brain 

The Olfactory Tract lies on the inferior aspect of the frontal 
lobe near the median plane. Its anterior extremity is enlarged 
to form the olfactory lull, which is joined by the olfactory 
nerves from the mucous membrane of the nose. Congenital 



16 THE NERVOUS SYSTEM 

absence of the olfactory nerves is one of the stated causes 
of anosmia. 

The frontal lobes are separated from one another by the 
great longitudinal fissure. On the basal surface of the brain, 
the posterior part of this fissure is hidden by the optic chiasma 
(Fig. 8), from which the optic nerves arise anteriorly and the 
optic tracts posteriorly. The tracts pass backwards and laterally 
round the mid-brain to reach the lower visual centres (p. 51). 

The interpeduncular fossa is bounded by the optic chiasma 
in front, by the mid-brain behind, and by the optic tract on 
each side. Its most anterior part is termed the tuber cinereum 
and it gives attachment to the stalk of the hypophysis {pituitary 
body). Behind the tuber cinereum lie the two corpora mamill- 
laria, one on each side of the median plane. The posterior 
perforated substance occupies the posterior angle of the inter- 
peduncular fossa. 

The structures included in this area on the basal surface 
of the brain form the anterior part of the floor of the third 
ventricle, and this statement may be confirmed by reference 
to Fig. 5. 

The anterior perforated substance (ant. perf. spot) lies lateral 
to the optic chiasma and forms the floor of the angle 
between the optic nerve and the optic tract. Its relationship 
to the internal carotid and the middle cerebral arteries is 
referred to on page 119. It may be noted that, whereas the 
posterior perforated substance lies in the median plane, the 
anterior perforated substance is bilateral. Both areas are 
pierced by small blood-vessels. 

The uncus is a well-marked elevation which lies postero- 
medial to the temporal pole and lateral to the anterior per- 
forated substance. It forms the anterior extremity of the 
hippocampal gyrus and so is part of the gyrus fornicatus 
(limbic lobe). It is said to contain the higher centres for the 
sense of smell. 

On its lateral side, the hippocampal gyrus is bounded by 
the collateral fissure, which is separated from the calcarine 



THE CEREBRUM 



17 







Fig. 8.- 


-Th 


e Inferior Aspect 


of 


the Brain. 


I. 


Frontal pole. 


n. 


Cerebral peduncle 


[cms 


23- 


Olfactory bulb. 


2. 


Temporal lobe. 




cerebri). 






24- 


Optic chiasma. 


3- 


Occipital pole. 


12. 


Pons. 






25- 


Oculo-motor nerve. 


4- 


Longitudinal fissure, an- 


'3- 


Medulla oblongata. 






26. 


Trochlear nerve. 




terior extremity. 


14. 


Pyramid. 






27. 


Trigeminal nerve. 


S- 


Longitudinal fissure, pos- 


IS- 


Olive. 






28. 


Abducent nerve. 




terior extremity. 


16. 


Restiform body. 






29. 


Facial nerve. 


6. 


Lat. fissure (of Sylvius). 


'7- 


Cerebellar hemisphere. 




3°- 


Acoustic nerve. 


7- 


Anterior perforated sub- 
stance. 


18. 


Posterior cerebel 
notch. 


ax 




3i- 


Glosso - pharyngeal 
nerve. 


8. 


Optic tract. 


19. 


Gyrus rectus. 






32- 


Vagus nerve. 


9- 


Corpus mamillare. 


20. 


Orbital gyri. 






33- 


Accessory nerve. 


10. 


Posterior perforated sub- 


21. 


Tuber cinereum. 






34- 


Hypoglossal nerve. 




stance. 


22. 


Olfactory tract. 






35- 


Orbital gyri. 



i8 



THE NERVOUS SYSTEM 



fissure posteriorly by the lingual gyrus (Fig. 9). The latter 
is believed by some authorities to contain the higher centres 
for the sense of taste. 

The other cortical areas on the basal surface of the brain 
need not be specially described, since little is known with 
regard to the functions which they subserve. 




Fig. 9. — Medial Aspect of Right Cerebral Hemisphere. 

17. Uncus. 

19. Calcarine fissure. 



20. Collateral fissure. 

21. Lingual gyrus. 



The Mesencephalon or Mid- Brain, which forms the upper- 
most part of the brain-stem, constitutes the connexion 
between the cerebral hemispheres and the pons. It consists 
of the four corpora quadrigemina, which lie on its dorsal aspect, 
and the cerebral peduncles, which are partially separated from 
one another anteriorly by a deep notch. The upper pair of 
the corpora quadrigemina are connected with the optic tracts 
(p. 51), while the lower pair are connected with the auditory 
tracts (p. 89). The cerebral peduncle consists of a dorsal 
part or teg?nentum, which is continuous across the median 
plane, and a ventral part or basis pedunculi (crusta), which is 



THE MID-BRAIN 



19 



separated from the corresponding part by the notch above 
mentioned (Fig. 10). A small oval elevation, termed the 



Cerebral aqueduct (of Sylvius) 
1 



Oculomotor nucleus--/ 



Mesial fillet _ _ 




Motor fibres' 



Oculo-motor nerve 

Fig. 10. — Transverse Section through the Mid-Brain, showing the dorsal 
portion, or tegmentum, which is separated, from the ventral portion, 
or basis pedunculi, by the substantia nigra. 



Optic tract 



Lateral geniculate bod\ v^ 



Medial geniculate bod} 

Pulvinar 



Corpora quadiigemina — -- 




Optic 
nerve 



Mid-brain 

Corpus mamillare 



■O \ Trigeminal nerve 

E2 Pons 

JW. Facial nerve 




Fig. 11. — The Lateral Aspect of the Brain-Stem. 

medial geniculate body, is placed on the lateral aspect of the 
cerebral peduncle and is partially overhung by the projecting 
posterior end of the thalamus (Fig. 11). It is connected 






20 



THE NERVOUS SYSTEM 



with the auditory tract, and the grey matter which it contains 
constitutes one of the lower auditory centres. 

The third {oculo-motor) and fourth {trochlear) cerebral nerves 
emerge from the surface of the mid-brain. The former 
appears on the anterior aspect, but the latter leaves the dorsal 
aspect just below the inferior pair of corpora quadrigemina. 

The Pons is interposed between the mid-brain above and 
the medulla oblongata below. Laterally, it is connected to 







a 



nrr: 



'is. vmv 



\W 



■mm 




Fig. 12. — The Anterior Aspect of the Brain-Stem. 



i. Pons. 

2. Trigeminal nerve. 

3. Brachium pontis. 

4. Medulla oblongata. 

5. Pyramid. 



6. Olive. 

7. Superficial arcuate fibres. 

8. Restiform body. 

9. Mid-brain. 

10. Lateral geniculate body. 



the cerebellar hemispheres by the brachia pontis {middle 
cerebellar peduncles). Its anterior surface bulges forwards and 



THE MEDULLA OBLONGATA 21 

presents a transversely striated appearance, which indicates the 
direction taken by its superficial fibres (Fig. 12). The dorsal 
surface of the pons forms the upper part of the floor of the 
fourth ventricle (Fig. 32). 

The fifth, sixth, seventh and eighth cerebral nerves are all 
connected with the anterior surface of the pons. The 
fifth emerges from the brain-stem near the upper border of 
the pons, at its junction with the brachium pontis. The 
sixth emerges near the median plane, in the groove between 
the pons and the medulla oblongata. The seventh and eighth 
are connected to the same groove but lie farther away from 
the median plane (Fig. 8). 

The Medulla Oblongata connects the pons above to the 
spinal medulla below. Its anterior surface is marked by two 
elongated elevations, which are termed the pyramids. They 
lie one on each side of the median plane and they are produced 
by the underlying pyramidal tracts. At a lower level the 
superficial part of the decussation of the pyramids can some- 
times be made out in the median plane (Fig. 12). A second 
elevation is situated lateral to the pyramid and separated 
from it by a groove in which the fibres of the twelfth {hypo- 
glossal) ?ierve emerge. It is termed the olive, and is produced 
by a mass of grey matter, known as the olivary nucleus. The 
restiform body forms a surface elevation on the lateral aspect 
of the medulla oblongata. It is separated from the olive by 
a longitudinal groove, in which the fibres of the ninth, tenth 
and eleventh cerebral nerves emerge from the brain-stem. 
(Fig. 8). Most of the tracts which constitute the restiform 
body pass upwards into the cerebellum. 

The dorsal surface of the medulla oblongata in its upper 
part forms the lower portion of the floor of the fourth 
ventricle. 

The Cerebellum lies in the posterior cranial fossa below the 
posterior, parts of the cerebral hemispheres, from which it is 



22 THE NERVOUS SYSTEM 

separated by a fold of dura mater, termed the tentorium 
cerebelli (p. 109). It consists of a narrow central portion, 
known as the vermis, and two lateral hemispheres. The 
cerebellum establishes connexions with the spinal medulla 
and the medulla oblongata by means of the restiform bodies, 
with the pons by means of the brachia pontis (middle peduncles), 
and with the mid-brain and cerebrum by the brachia con- 
junctiva (superior peduncles). The term " cerebellopontine 
angle " is sometimes used to indicate the region where the 
brachium pontis enters the substance of the cerebellum 
(Fig. 12). 

The cerebellum exercises a controlling influence over 
muscular tonus, and its cortex is intimately connected with 
the cortex of the motor area of the cerebrum. The latter, 
however, governs the muscles of the opposite side of the 
body, whereas the cortex of the lateral cerebellar hemisphere 
is related £o the homo-lateral muscles. Cerebellar lesions are 
accompanied by incoordination and loss of equilibrating 
power and are typically characterised by a reeling, staggering 
gait. In the case of the cerebellum, as in the case of the 
brain, the symptoms are modified by the mode of onset of 
the lesion, and they are not so distinctive in slow-growing 
tumours as they are when the onset is more rapid. In the 
latter case, the patient tends to fall towards the side of 
the lesion, owing to the loss of tonus in the homo-lateral 
muscles, but in slowly progressing cases the patient learns to 
appreciate the tendency and often counteracts too strongly, 
so that he falls (or deviates in walking) to the opposite side. 

Owing to the loss of tonus control, more work is thrown on 
the motor cortex of the cerebrum than it is able to perform 
efficiently. As a result, intentional tremor may be well-marked 
in cerebellar lesions. 

In unilateral irritative lesions of the cerebellar cortex, cere- 
bellar fits may occur. They are characterised by tonic spasms, 
most marked in the homo-lateral limbs. 

In lesions of the vermis, retraction of the head and arching 



THE LATERAL VENTRICLES 23 

of the back have been noticed, but the opposite movements 
have also been observed in similar cases. 

The blood-supply of the cerebellum is derived from the 
basilar and the two vertebral arteries (p. 120). Cerebellar 
haemorrhage, though not a common lesion, is of importance 
owing to the proximity of the fourth ventricle and the im- 
portant centres in its floor (Fig. 5). The veins of the 
cerebellum terminate in the transverse (lateral) and other 
cranial blood-sinuses (p. 114). Septic infection may spread 
from the tympanic (mastoid) antrum, through the transverse 
sinus and cerebellar veins, and so give rise to abscess 
formation. 

The Internal Structure of the Brain 

The Lateral Ventricles of the brain are roofed in by the 
corpus callosum, which is covered on its inferior surface 
with ependyma. When the roof of the lateral ventricle is 
removed, the free surface of the caudate nucleus is exposed 
(Fig. 13). Its enlarged anterior extremity, or head, forms a 
prominent elevation in the anterior part of the floor of the 
ventricle, but, as it is traced backwards, it diminishes rapidly in 
size ; at the same time, it arches upwards and laterally, so that, 
in a horizontal transverse section of the brain, the head of the 
caudate nucleus is cut through in front and the tail behind, 
but, owing to its upward bend, the body does not appear in 
the section (Fig. 18). 

The superior surface of the thalamus lies in the floor of the 
ventricle to the medial side of the body of the caudate 
nucleus. It is overlapped by the free lateral margin of the 
tela chorioidea (velum interpositum) (p. 26), which contains the 
veins of the chorioid plexus. The serum which is transuded 
from the veins of this plexus through the ependyma into the 
lateral ventricle constitutes the cerebrospinal fluid. This fluid 
circulates through the ventricular system and ultimately drains 
away into the subarachnoid space (p. in). Excessive secretion 



2 4 



THE NERVOUS SYSTEM 



of the fluid is one of the causes of hydrocephalus ; and, in 
this condition, the whole ventricular system may become 
enormously dilated. 




Fig. 13. — Dissection to show the Floor of the Lateral Ventricle. 
(Turner's Anatomy. ) 

The roof of the lateral ventricle has been removed, along with the greater part of the 
septum pellucidum. In addition the fornix has been divided and turned back- 
wards, exposing the tela chorioidea (velum interpositum). 

n. Fornix. 
b, c. Columns of fornix. 

d. Tela chorioidea 

e. Corpus callosum, 

genu. 



/. Caudate nucleus. 

g. Stria terminalis (taenia 

semicircularis). 
/;. Thalamus. 
/. Fimbria. 



«/. Hippocampus. 
n Bulbus cornu. 
o. Trigonum collaterale 
(ventriculi). 



The tela chorioidea is itself overlapped by the free lateral 
edge of the fornix. The body of the fornix consists of 



THE LATERAL VENTRICLES 



25 



a flattened band of white fibres and its narrow anterior 
extremity divides into the two columns {anterior pillars) 
(p. 15). The posterior extremity of the fornix divides into 
two crura, which pass downwards and forwards in the floor of 
the inferior (descending) horn of the lateral ventricle to 



Corpus callo=um 



Septum pelkiL 



Interventricular foramen — ""' 
Lamina terminalis 



Oculo-motor nerve 



— Middle commissure 



Pineal body 
Corpora quadrigemina 
__ _ Cerebral aqueduct 
(of Sylvius). 



Fourth 

" ventricle 




_ __ _ Central canal of 
spinal medulla 



Fig. 14. — Median Sagittal Section through the Brain-Stem, showing the 
third and fourth ventricles and their connexions. 



terminate in the uncus (p. 16). Superiorly, the fornix is 
attached to the septum pellucidum in front and to the corpus 
callosum behind (Fig. 14). Inferiorly, it is in contact with 
the tela chorioidea, which separates it from the superior surface 
of the thalamus on each side and from the third ventricle in 
the median plane. 



26 



THE NERVOUS SYSTEM 



The medial wall of the lateral ventricle is formed, anteriorly, 
by the septum pellucidum, and, posteriorly, by the union of 
the fornix with the corpus callosum. The interventricular 
foramen (of Monro), which connects the lateral with the third 
ventricle, is situated on this wall behind the column (anterior 







Fig. 15. — The Tela Chorioidea (velum interpositum) viewed from above. 

5. Septum pellucidum (cut). 

6. Vein of corpus striatum. 

7. Stria terminalis. 
S. Great cerebral vein (of Galen). 

9. Internal cerebral vein. 



1. Tela chorioidea. 

2. Chorioid plexus. 

3. Thalamus. 

4. Caudate nucleus. 



pillar) of the fornix and in front of the anterior extremity of 
the thalamus. 

When the corpus callosum, the septum pellucidum, and 
the fornix are completely removed, the cavities of the two 
lateral ventricles are thrown into one and the tela chorioidea 
(velum interpositum) is exposed in its entirety (Fig. 13). It 



THE LATERAL VENTRICLES 27 

is triangular in outline and its apex lies at the interventricular 
foramina. It extends from the one side of the median plane 
to the other and partially overlaps both thalami. In the 
median plane the tela chorioidea is stretched across the gap 
between the two thalami, and, in this situation, it forms the 
roof of the third ventricle. Between its two layers the internal 
cerebral vein {of Galen) passes backwards. It is formed at the 
interventricular foramen by the union of the vein of the 
corpus striatum (p. 29) with a vein from the chorioid plexus. 
At the posterior end of the tela chorioidea the two internal 
cerebral veins unite to form the great cerebral vein {of Galen) 
(Fig. 15), which emerges below the splenium of the corpus 
callosum and above the dorsal aspect of the mid-brain and 
terminates in the straight sinus. 

Tumours of the cerebellum or of the corpora quadrigemina 
may obstruct the great cerebral vein near its termination (Fig. 55) 
and so produce engorgement of the veins of the chorioid plexus. 
As a result of this venous stasis, an increased amount of serum 
is transuded into the cerebral ventricles, giving rise to the 
condition of acquired hydrocephalus. 

Prolongations of the lateral ventricle extend backwards into the 
occipital lobe and downwards into the temporal lobe and form, 
respectively, the posterior and the inferior {descending) horns. 

The lateral ventricle may be tapped by passing in a special 
trochar and cannula at a point two fingers'-breadth in front 
of the mid-point of the line joining the glabella (p. 7) to the 
external occipital protuberance and about the same distance 
from the median plane (Fig. 16). The instrument is passed 
downwards and backwards for from i| to 2 inches before it 
enters the ventricle (Kocher). The course taken by the 
instrument is planned so as to avoid the motor cortex and 
the middle frontal gyrus. 

The inferior horn may also be reached from the surface 
without damage to the important cortical areas. The instru- 
ment is inserted at a point two fingers'-breadth behind the 
external acoustic meatus and the same distance above a line 



28 



THE NERVOUS SYSTEM 



drawn backwards from the lower border of the orbit through the 
centre of the external acoustic meatus (Fig. 16). It is directed 
medially and slightly upwards and forwards and passes below 
the higher auditory centres in the superior temporal gyrus. 
In the normal subject the inferior horn lies at a depth of 




Fig. 16. 



-Lateral Aspect of Skull, showing the relations of important 
structures to the surface. 



12. Line drawn from floor of orbit through 
centre of external acoustic meatus. 
o 1 . Site for puncture of lateral ventricle. 



o- Site for puncture of inferior horn of 
lateral ventricle. 



2 inches from the surface, but when the ventricles are dis- 
tended, the brain substance may be greatly thinned out. 



The Third Ventricle is situated in the median plane and 
its lateral walls are formed by the two thalami. Anteriorly, 
it is closed by the lamina rostra/is, which extends from the 
rostrum of the corpus callosum to the optic chiasma (Fig. 6). 
This sheet of grey matter represents the anterior, or cephalic, 
extremity of the primitive neural tube (p. 2). The floor of 
the ventricle is formed by the structures which occupy the 



THE BASAL GANGLIA 



29 



interpeduncular fossa (p. 16) and, posteriorly, by the grooved 
upper surface of the mid-brain. The roof is formed by the 
tela chorioidea (velum interpositum) and, above that, by the 
fornix and the corpus callosum (Fig. 14). 



The Basal Ganglia are masses of grey matter, which are 
more or less completely embedded in the substance of the 
brain near its basal surface. Their cells act as cell-stations 
for both afferent and efferent fibres of the cerebral cortex. 



Optic tract 



Optic 



Lateral geniculate bodj ~}j^~~Z. 



Medial geniculate body- 
Pulvinar ■ 



Corpora quadrigemina 




— Mid -brain 
■ -Corpus mamillare 

^_ \ Trigeminal nerve 

- Pons 
Facial nerve 



Fig. 17. — The Lateral aspect of the Brain-Stem. 

The basal ganglia comprise (1) the thalamus, and (2) the 
corpus striatum, which is further subdivided into the caudate 
and the lentiform (lenticular) nuclei. 

1. The Thalamus lies directly above, and is continuous 
with, one-half of the peduncle of the mid-brain, but projects 
beyond it both anteriorly and posteriorly. When viewed 
from above, it is seen to be somewhat triangular in outline 
and its postero-medial angle shows a distinct enlargement, 
which is termed the pulvinar. The postero-lateral angle, 
which overhangs the lateral aspect of the mid-brain, possesses 



30 THE NERVOUS SYSTEM 

a similar elevation on its inferior surface. This elevation is 
termed the lateral geniculate body, and both it and the pulvinar 
receive afferent fibres from the optic tract (Fig. 17). 

The superior surface of the thalamus has been mentioned 
(p. 23) in connexion with the floor of the lateral ventricle, 
and the medial surface in connexion with the lateral wall of 
the third ventricle (p. 28). Its lateral surface (Fig. 18) is 
in contact with the fibres of the internal capsule (p. 32). 
Owing to this latter relationship, the functions of the thalamus 
are extremely difficult to determine, as lesions are rarely 
restricted to the thalamus itself, and the possible involvement 
of the internal capsule cannot be excluded. 

Lesions in the posterior part of the thalamus usually affect 
the pulvinar and the lateral geniculate body, and consequently 
produce homonymous hemianopia (p. 52). In addition, there 
is usually some degree of motor paralysis and of hemi- 
anesthesia. Loss of deep sensibility is frequently co-existent 
with thalamic lesions and it is often accompanied by astereo- 
gnosis and loss of muscle and joint sense. How far these 
symptoms are due to involvement of the internal capsule, it is 
at present impossible to determine. 

2. The Caudate Nucleus (p. 23) and (3) the Lentiform 
Nucleus will be referred to in the description of the internal 
capsule (vide infra). 

The precise functions of these nuclei are not yet understood. 
Bilateral lesions, e.g. progressive softening, of the lentiform 
nuclei cause difficulty in articulation and tremors and spasticity 
in the muscles of the trunk and lower limbs. Cases of this 
kind have been recorded in which careful examination has 
failed to detect any affection of the internal capsule. 

Sections through the Brain 

In Horizontal Transverse Sections made through the 
cerebral hemisphere at the level of the interventricular 
foramen, the island (of Reil) forms a conspicuous landmark. 



SECTIONS THROUGH THE BRAIN 31 

It may be recognised as a submerged area of cerebral cortex, 
which is situated nearer to the frontal than to the occipital 
pole and is overlapped by the adjoining cortical areas (Fig. 



/ 



X 






9- 

10 • 



II 



12 — — 



14- 




-4 



Fig. 18. — Horizontal Section through Left Cerebral Hemisphere. 






1. Island (of Reil). 

2. Lentiform nucleus. 

3. Claustrum. 

4. Posterior horn of iateral 

ventricle. 

5. Corpus callosum. 



6. Anterior liorn of lateral 

ventricle. 

7. Septum pel lucid um. 

8. Caudate nucleus. 

g. Internal capsule, an- 
terior limb. 



10. Column of fornix. 

11. Internal capsule, genu. 

12. Internal capsule (motor 

fibres). 

13. Thalamus. 

14. Internal c spsule (sen- 

sory fibres). 



18). On the deep surface of the white matter of the island, 
and almost co-extensive with it, a thin sheet of grey matter is 
cut through. This is termed the claustrum, and it is separ- 
ated from the lentiform nucleus by a narrow strip of white 




32 THE NERVOUS SYSTEM 

matter, which is known as the external capsule. The lentiform 
nucleus, which resembles a biconvex lens in shape, is com- 
pletely embedded in the substance of the cerebral hemisphere, 
and its medial surface is in contact with a broad band of white 
matter, termed the internal capsule. As seen in a horizontal 
section the internal capsule consists of two limbs which 
meet one another at a bend or genu. The shorter anterior 
limb lies between the lentiform nucleus and the head 
of the caudate nucleus, by which it is separated from the 
anterior part of the lateral ventricle ; the longer, posterior 

| 

f 



Caudate nucleus 
,.-"']_,- Corpus callosum 

- Lateral ventricle 

- Internal capsule 
— ■""*"* J. - - Thalamus 

Island (of Reil) '^'^'^ 

Claustrum ' 
External capsule 
entiform nucleus 



Fig. 19. — Frontal (Coronal) Section through Left Cerebral Hemisphere. 

limb is closely applied to the lateral aspect of the thalamus 
(Fig. iS). 

In a Frontal (Coronal) Section made through the cerebral 
hemisphere opposite the anterior perforated substance (spot), 
the island, the claustrum, and the external capsule can all be 
readily identified (Fig. 19). When the lentiform nucleus is 
examined in such a section, its lower part is seen to become 
continuous with the grey matter of the anterior perforated 
substance, and, consequently, the arteries which enter the 
brain at this point at once come into relationship with the 




THE INTERNAL CAPSULE 33 

nucleus. The fibres of the internal capsule can be traced 
down from the cortex above into the ventral portion of the 
cerebral peduncle, and in their course they pass between 
the lentiform nucleus, on the lateral side, and the caudate 
nucleus and the thalamus, on the medial side. The arteries 
which supply the basal ganglia and the internal capsule 
arise from the middle cerebral (p. 119), as it lies below the 
anterior perforated substance, and they pass upwards over the 
lateral aspect of the lentiform nucleus. They bend medially 
and pierce the nucleus, giving it numerous branches. There- 
after they traverse the internal capsule and terminate on the 
caudate nucleus and the thalamus. The artery of cerebral 
hemorrhage passes through the internal capsule a little behind 
the genu. 

The motor fibres, which arise in the cortex of the anterior 
central gyrus, converge as they pass towards the internal 
capsule. And, at the same time, the fibres connected with 
the uppermost part of the gyrus incline backwards, while those 
connected with its lowermost part incline forwards. As a 
result, the motor fibres for the muscles of the tongue, face 
and head come to occupy the genu of the internal capsule, 
and lie in front of the fibres for the upper limb. Behind the 
fibres for the upper limb lie the motor fibres for the muscles 
of the trunk, while the fibres for the lower limb extend as 
far backwards as the middle of the posterior limb of the 
internal capsule. 

In this part of the brain, therefore, all the motor fibres are 
crowded together in the genu and the anterior half of the 
posterior limb of the capsule, and it is probable that many 
sensory fibres accompany them. It must be remembered that 
all these fibres cross the median plane, either in the brain- 
stem or in the spinal medulla, before they reach their ultimate 
destinations, and that lesions of the internal capsule, therefore, 
produce their effects on the opposite side of the body. When 
the " artery of cerebral haemorrhage " ruptures, the extrava- 
sated blood presses on the fibres in the anterior half of 



34 



THE NERVOUS SYSTEM 



the posterior limb of the capsule. Owing to the crowding 
together of the motor fibres, a very small haemorrhage may be 
sufficient to cause complete hemiplegia, and, in addition, 
irregularly distributed areas of sensory disturbance. Clinical 
evidence shows that certain muscles very constantly remained 
unaffected or only slightly affected in lesions of the internal 
capsule. The diaphragm and other muscles of the trunk, and 




j\w l|l ll|ll 



mm 



Fig. 20. — Diagram to illustrate Innervation of a Muscle by both 
Cerebral Hemispheres. 



1. Muscle. 2. Motor nucleus. 

3. Hetero-lateral upper neurone. 



4. Homo-lateral upper neurone. 

5. Cortex. 



the muscles of the upper part of the face, are not paralysed. 
This immunity is explained on the grounds that muscles which 
are accustomed to act together are bilaterally represented in 
the cortex, and their motor fibres, therefore, descend in the 
internal capsules of both cerebral hemispheres (Broadbent's 
law). The same explanation accounts for the relatively 
smaller degree of paralysis in the lower limbs as compared 
with the upper limbs. 



THE INTERNAL CAPSULE 35 

The anterior limb of the internal capsule is occupied chiefly 
by fibres which connect the cortex of the frontal lobe with 
the grey matter of the pons, and nothing is known concerning 
their function. 

The posterior or retro-lenticular part of the posterior limb 
contains — (1) Sensory fibres from the opposite side of the 
body; (2) the acoustic radiation, which extends from the 
lower acoustic centres to the cortex of the superior temporal 
gyrus; (3) the optic radiation, which lies behind (1) and 
(2), extending from the lower visual centres (p. 51) to the 
occipital cortex. It is probable that the fibres of the other 
special senses, namely, taste and smell, also pass through 
the posterior third of the posterior limb of the internal 
capsule. 

The manner in which the fibres of the internal capsule 
converge below and spread out above is well shown in 
Fig. 21, which represents a dissection carried out from the 
lateral aspect of the brain. The cortical areas which overlap 
the island (of Reil), the island itself, the claustrum, the 
external capsule and the lentiform nucleus have all been 
removed. The connexions of the capsule with the different 
parts of the cortex are clearly indicated, and it is evident that 
the lower the position of a lesion, the more complicated and 
widespread will be its effects. 

A lesion of the internal capsule may be due to pressure, 
from tumour growth, haemorrhage, etc., or to anaemia, following 
occlusion of the vessels of supply. When of large extent, it 
is accompanied by complete hemiplegia, hemi-anaesthesia, loss 
of muscle and joint sense, and deafness, all on the opposite 
side, and homonymous hemianopia affecting the corresponding 
sides of the retinae. A smaller haemorrhage may produce 
complete hemiplegia, with irregular sensory phenomena which 
are never confined to one limb. 

A lesion of the postero-lateral part of the thalamus causes 
hemi-anaesthesia of the whole of the opposite half of the body. 
The condition is usually associated with disturbances of vision 



36 THE NERVOUS SYSTEM 

or with motor paralysis which is most marked in the lower 
limb. 

Lesions of limited extent in the region of the genu produce 
a condition which has been termed pseudo-bulbar paralysis, 




Fig. 21. — Dissection of Brain, showing the Lateral Aspect of the 

Internal Capsule. 

Note. — The overlying cortex, the claustrum, the external capsule and the lentiform 
nucleus have all heen removed. 



I. 


Internal capsule. 


6. 


Optic nerve. 


n. 


Oculo-motor nerves. 


2. 


Corona radiata. 


7- 


Optic tract. 


12. 


Trochlear nerve. 


3- 


Optic radiation. 


8. 


Uncus. 


13- 


Pons. 


4- 


Anterior commissure. 


9- 


Temporal pole. 


14- 


Motor fibres in pons 


5- 


Olfactory hulh. 


io. 


Mid -brain. 
16. Olive. 


15- 


Pyramid. 



the fibres implicated being those destined for the tongue, 
palate, etc. It is said that this condition may be caused by 
unilateral lesions, but there is a disposition to believe that 
the lesion is bilateral or that, if unilateral, it is accompanied 






THE PYRAMIDAL TRACT 37 

by small lesions in the medulla oblongata (see bulbar paralysis, 
p. 108). 

The Path of the Motor Fibres. — The motor fibres have 
already been traced from their origin in the anterior central 
gyrus, through an intermediate area termed the corona radiata 
(Fig. 21), into the internal capsule. Lesions of the corona 
radiata tend to resemble cortical lesions in their distribution, 
as, unless situated immediately above the internal capsule, 
they never produce complete hemiplegia (p. 6). Irritative 
lesions affecting the corona radiata alone differ from similar 
cortical conditions in that they cause tonic instead of clonic 
muscular spasms. 

From the internal capsule, the motor fibres pass directly 
into the basis pedunculi (crusta of the mid-brain, Fig. 21), 
where they form a compact bundle, which is termed the 
pyramidal tract. At the lower border of the mid-brain, the 
pyramidal tract enters the ventral portion of the pons, and 
is there broken up into a number of small bundles by the 
grey matter and the transverse fibres of the pons. These 
separate bundles are reassembled below, and they descend 
through the ventral part of the medulla oblongata, forming 
the surface elevation which is termed the pyramid. 

In the lower part of the medulla oblongata, the great 
majority of the fibres of the pyramidal tract pass backwards 
and cross the median plane. As they do so, they intersect 
the corresponding fibres of the opposite side, and the general 
arrangement is referred to as the decussation of the pyramids. 
These fibres, now known as the lateral or crossed pyramidal 
tract, descend in the lateral funiculus (column) of the spinal 
medulla and terminate by arborising round the cells of the 
posterior column (cornu) of grey matter. These cells send 
their fibres forwards to end round the cells of the anterior 
column, and these in turn give rise to the fibres which 
constitute the anterior roots of the spinal nerves. Thus, 
three neurones are concerned in the passage of stimuli from 
the cerebral cortex to the muscles. 



3« 



THE NERVOUS SYSTEM 



Those fibres which do not take part in the decussation of 
the pyramids pass downwards in the anterior funiculus of the 
spinal medulla (Fig. 25), forming the direct or anterior 
pyramidal tract. It is probable that all these fibres cross the 



Corpus callosunv 
Caudate nucleus 



Thalamus' 

Motor fibres in internal' 
capsule 




Island (of Reil) 



Lentiform nucleus 



Decussation of 

pyramids 



Fig. 22. — Diagram of Frontal (Coronal) Section of Right Cerebral 
Hemisphere and Brain-Stem, showing the path of the Motor Fibres. 

In addition to the decussation of the pyramids, the numerous smaller decussations in 
connexion with the motor cerebral nerves are indicated in the diagram. 

median plane at various levels in the spinal medulla and that 
they terminate in the same way as the fibres of the crossed 
pyramidal tract. 

In addition to the decussations which have just been de- 
scribed, numerous smaller decussations occur at a higher level. 



CROSSED PARALYSIS 39 

As the pyramidal tract passes down through the brain-stem, 
the fibres which are destined for the nuclei of the motor 
cerebral nerves leave it at different points and cross the 
median plane to reach their objective (Fig. 22). In doing 
so they decussate with the corresponding fibres of the opposite 
side. This arrangement, together with the fact that the 
pyramidal tract is placed at no great distance from the cerebral 
motor nuclei, offers an explanation for the occurrence of 
crossed paralysis. 

The nucleus of the third cerebral (pculo-motor) nerve is 
placed in the mid-brain opposite the superior corpora quadri- 
gemina, and the fibres which it obtains from the pyramidal 
tract decussate at a slightly higher level. If a small localised 
haemorrhage occurs in the mid-brain at the level of the oculo- 
motor nucleus, it will involve the pyramidal tract after it has 
given off its fibres to the third nucleus of the opposite side. 
Such a haemorrhage, however, may readily involve the oculo- 
motor nucleus on the same side, and a crossed paralysis results. 
The lower cerebral nerves and the spinal nerves are paralysed 
on the opposite side of the body, while the oculo-motor nerve 
is paralysed on the same side as the lesion. The oculomotor 
nerve of the opposite side escapes because the lesion occurs 
below the point where its fibres leave the pyramidal tract and 
is not large enough to affect the structures in the opposite half 
of the mid-brain. This variety of crossed paralysis is some- 
times referred to as the syndrome of Weber. 

Theoretically, similar crossed paralyses may occur affecting 
any one of the motor cerebral nerves, but the only one of 
common occurrence is that in which facial paralysis exists on 
one side while the limbs are paralysed on the opposite side of 
the body. In this case, the lesion is placed in the pons at the 
level of the facial nucleus, and it is complicated by the fact 
that the nucleus of the sixth nerve and the sensory nucleus 
of the fifth are also likely to be involved (Fig. 23). The 
condition is described in detail on page 86. 

The structure of the various parts of the brain-stem and the 



4° 



THE NERVOUS SYSTEM 



results of lesions of the brain-stem will be dealt with when the 
nuclei of the individual cerebral nerves are described. 

The Spinal Medulla (Spinal Cord) begins at the foramen 
magnum, where it is continuous with the medulla oblongata, 
and extends downwards through the vertebral canal to the 
lower border of the first lumbar vertebra. In the lower 
cervical and the lower thoracic regions, the spinal medulla 




Facial 



Motor fibres 
Fig. 23. — Transverse Section through the Pons (Diagrammatic). 

increases in size, and these localised areas of enlargement 
correspond to the segments of origin of the great limb 
plexuses. 

Owing to the relative disproportion in length between the 
spinal medulla and the vertebral canal, the nerve-roots must 
arise from the spinal medulla at a much higher level than the 
intervertebral foramina through which they pass. Below the 
lower end of the spinal medulla, therefore, the vertebral canal 
is occupied by the nerve-roots of the lumbar, sacral, and 
coccygeal nerves, which together constitute the cauda equi?ia. 

The lower lumbar region of the vertebral canal is selected as 



LUMBAR PUNCTURE 41 

the site for the operation of lumbar puncture, because (1) the 
site chosen should provide a free flow of the cerebro-spinal 
fluid; (2) there is no danger of injuring the delicate spinal 
medulla; (3) the spaces between contiguous laminae is greatest 
in this region. There is little danger of injuring the nerve- 
roots of the cauda equina, as they tend to be pushed aside by 
the point of the needle. 

The space between the fourth and fifth laminae may be 
chosen, or the space between the fifth and the sacrum. Some 
authorities prefer to enter the needle in the posterior median 
line. In that case, the instrument passes between two con- 
secutive spines instead of through the interlaminar interval. It 
must be remembered that the fourth lumbar vertebra lies on 
the line joining the highest points on the iliac crests. When 
the interlaminar interval between the fourth and fifth lumbar 
vertebrae is selected, the needle is inserted about half an inch 
below this line and rather less than one inch from the median 
plane, and it is thrust in a forward and slightly medial direction. 
If the point of the needle meets bone, it must be partially 
withdrawn and then re-inserted, after some alteration has been 
made in its direction. When the interlaminar interval is 
gained, the operator experiences the characteristic resistance 
due to the strong ligamentum flavum, which fills in the gap 
between the laminae. In the adult, the instrument will require 
to be introduced to a depth of about two inches before it 
reaches the vertebral canal, but in the young child the distance 
is rather less than one inch. 

In order to separate the laminae as far as possible, the 
patient should lie on his side with the body fully flexed, while 
the operation is being carried out. If the interspinous interval 
is chosen, the needle must be directed forwards and slightly 
upwards, parallel to the inferior border of the spine. In this 
case, the strong supra-spinous ligament must first be pierced 
and the instrument then passes forwards through or by the 
side of the interspinous ligament, before it enters the canal. 

After the needle has been successfully passed into the canal, 



4 2 



THE NERVOUS SYSTEM 



the dura mater must be traversed before any fluid can be 
obtained. Whether the fluid obtained is derived from the 
subdural or from the subarachnoid space seems to be im- 
material. 

Intracranial Tension. — Although it is impossible to deter- 
mine the condition of the intracranial tension in the adult 
unless lumbar puncture is performed, it is quite easy to do 
so in the infant, owing to the presence of the anterior fontanelle. 



Occiput 



J>ost 
"Fontanelle 




Fig. 24.— Fcetal Skull, seen from above. (Johnstone's Midwifery.) 

This area is situated at the meeting-place of the two parietal 
bones with the two halves of the frontal bone, and it forms a 
diamond-shaped gap in the skull (Fig. 24). When the intra- 
cranial tension is normal, the bony edges of the fontanelle can 
readily be palpated and a normal slight pulsation, which is 
transmitted from the base of the brain, can be felt. This 
pulsation becomes more noticeable when the intracranial 
tension is slightly increased, but it disappears entirely when 
the tension is greatly increased and also when it is lowered. 
Increased intracranial tension occurs in the acute fevers 



INTRACRANIAL TENSION 43 

and in cases of cerebral involvement, e.g., the intracranial 
hemorrhage of birth palsies. Cerebral symptoms induced 
refiexly by pathological conditions of other organs are not 
accompanied by any increase in intracranial tension. 

Sinking of the anterior fontanelle indicates a decrease in 
intracranial tension. It marks a diminution of vitality, and 
is of common occurrence in epidemic enteritis and other 
conditions which are accompanied by a loss of fluid from 
the body. 

The anterior fontanelle should be closed by the end of the 
second year. Delayed closure occurs in certain constitutional 
diseases, e.g. rickets, cretinism, etc.,. or it may be due to 
hydrocephalus or some other condition causing increased 
intracranial tension. If the anterior fontanelle closes too 
early, the condition of microcephalus results. 

The Structure of the Spinal Medulla is identical with the 
structure of the brain, but the arrangement of its constituent 
parts is somewhat different. The grey matter is situated 
centrally and consists of anterior and posterior columns {horns) ; 
the white matter, which consists of afferent and efferent 
tracts, completely surrounds the grey matter (Fig. 25). 

The posterior funiculus (columns of Goll and Burdach) of 
the spinal medulla lies between the posterior column of grey 
matter and the middle line. It contains a few tactile fibres 
and the fibres which convey joint and muscle sense. These 
latter arise in the nerve cells in the ganglia on the posterior 
nerve-roots of the spinal nerves and ascend, through the 
spinal medulla, to the medulla oblongata, where they establish 
connexions with the cerebellum. Above the level of the 
decussation of the pyramids, they cross the median plane 
and ascend through the pons and mid-brain to reach the 
thalamus. Their precise destination is not yet known, but 
they probabiy traverse the posterior part of the posterior 
limb of the internal capsule. 

In advanced cases of locomotor ataxia, joint-sense and 



44 



THE NERVOUS SYSTEM 



muscle-sense are both entirely lost, and, on post-mortem 
examination, the posterior funiculi are found to have under- 
gone complete degeneration. 

The lateral funiculus (column) lies to the lateral side of 
the columns of grey matter and contains, among others, the 
lateral pyramidal and the spina-thalamic tracts. The former, 
which undergoes decussation in the lower part of the medulla 
oblongata (p. 37), is distributed ultimately to the muscles of 




Fig. 25. — Transverse Section through Spinal Medulla (Schematic). 



I, II. Muscle and joint sense. 

III. Equilibration sense. 

IV. Motor tract (crossed). 

V. Painful, tactile and thermal 
sensibility. 



VI. Motor tract (uncrossed). 
VII. Anterior column of grey 
matter. 
VIII. Posterior column of grey 
matter. 



the same side of the body. The spino-thalamic tract is 
made up of the afferent fibres which convey painful, thermal 
and tactile sensations. These fibres enter the spinal medulla 
in the posterior nerve-roots and at once cross the middle line 
in the neighbourhood of the central canal (Fig. 26). They 
then ascend in the lateral funiculus to reach the thalamus and 
the posterior limb of the internal capsule, but little is known 
with reference to the cortical areas with which they are 
associated (p. 12). As the spino-thalamic tract passes up- 



LESIONS OF THE SPINAL MEDULLA 



45 



wards, it increases in size owing to the accession of new 
fibres. In the medulla oblongata and the pons, it receives 
fibres from the sensory nuclei of the cerebral nerves of the 
opposite side. 

Lesions in the medulla oblongata may affect the spino- 
thalamic tract together with one of the sensory cerebral nuclei, 
the fifth being most frequently involved (p. 61). The result- 
ing condition is akin to crossed paralysis (p. 39) and is termed 
alternate hemianesthesia^ because the anaesthesia affects the 




Flfi. 26. — Diagram to illustrate the course taken by Sensory Fibres 
after entering the Spinal Medulla. 



A. Spinothalamic tract (painful, thermal 

and tactile sensations). 

B. Posterior funiculus of spinal medulla 

(muscle and joint sense, and a few 
tactile fibres). 



C. Anterior nerve-root. 
\D. Posterior nerve-root. 

E. Anterior ramus (primary division). 

F. Posterior ramus. 

A". Typical spinal nerve. 



limbs of the opposite side and the trigeminal nerve on the 
same side as the lesion. 

In a Hemi-lesion of the Spinal Medulla in the mid-thoracic 
region, the lower limb of the same side is completely paralysed 
owing to the interruption of the lateral pyramidal tract, and, 
since it is the upper neurone which is affected, the paralysed 
muscles are spastic. In addition, there is loss of muscular 
and joint sense in the paralysed limb, since the fibres which 
convey these varieties of sensibility do not decussate until 
they reach the medulla oblongata. On the other hand, the 



46 THE NERVOUS SYSTEM 

conduction of painful, thermal and tactile sensations from 
the paralysed limb is not interfered with, since these fibres 
cross the median plane as soon as they enter the spinal 
medulla. The lower limb of the opposite side is not paralysed, 
but, since the spino-thalamic tract is involved, it is rendered 
completely anaesthetic to painful and thermal sensations and 
partially anaesthetic to tactile stimuli. Muscle sense, however, 
is unimpaired on the unparalysed side. 

Owing to the difference in length between the spinal 
medulla and the vertebral canal (p. 40), the upper limit of 
the anaesthetic area is considerably lower than the actual 
level of the lesion. At the level of the upper limit of 
anaesthesia, but on the paralysed side of the body, there is 
a narrow zone of complete anaesthesia. This condition is due 
to injury of the sensory fibres as they enter the spinal medulla, 
and it affects the same side as the lesion, since the fibres 
are implicated before they cross the middle line. 

The crossed motor and sensory paralysis which results from 
a hemi-lesion of the spinal medulla is known as Broivn- 
Sequard Paralysis. 

In Acute Anterior Poliomyelitis the lesion is confined to 
the anterior column of the grey matter of the spinal medulla 
and it consequently produces a purely motor paralysis. 
Further, it is usually restricted either to the cervical or the 
lumbar enlargement of the spinal medulla, but, in severe cases, 
it may be more widespread. The areas of grey matter affected 
by the lesion are identical with the areas supplied by the 
anterior spinal arteries, and it is believed that the organism 
which produces the disease reaches its destination by the 
blood-stream. 

Many of the muscles which are paralysed in the acute stage 
completely recover at a later period. The residual paralysis 
is of the lower neurone type (p. 3). Consequently, the para- 
lysed muscles are flaccid ; they undergo atrophy and their 
electrical reactions become altered. 

In Progressive Muscular Atrophy the lesion may commence 



LESIONS OF THE SPINAL MEDULLA 47 

in the motor tract and spread to the anterior column of grey 
matter in the spinal medulla, or it may commence in the 
anterior column and spread to the motor tract. In the first 
case, the initial symptoms are those of an upper neurone 
affection (p. 3), whereas in the second case they belong to 
the lower neurone type (p. 3). 

The lesion usually commences in the first thoracic segment 
of the spinal medulla, and, in consequence, the small muscles 
of the hand (p. 156) are the first to undergo atrophic changes. 
The disease gradually spreads upwards and downwards along 
the spinal medulla, and the muscles of the forearm, arm and 
trunk become similarly affected. The sterno-mastoid and the 
upper part of the trapezius (accessory nerve, p. 103) are 
attacked late in the disease, and their involvement indicates 
that the lesion is spreading to the medulla oblongata, where it 
affects the nuclei of the ninth, tenth, eleventh and twelfth 
cerebral nerves, causing bulbar paralysis (p. 108). It should 
be noted that the muscles of the face and the platysma, 
which are supplied by the facial nerve, are practically never 
involved. 

In Syringomyelia the lesion is situated near the base of the 
posterior column (cornu) of the grey matter. The cells in 
which the fibres of the pyramidal tract end (p. 37) may be 
affected, but the most characteristic symptoms are due to 
interference with the sensory path. Thermal and painful 
sensations are lost, since the fibres are interrupted as they 
traverse the grey matter to reach the other side of the spinal 
medulla. Tactile sensation, as a rule, is not affected, because 
many of the tactile fibres ascend in the posterior columns, 
without first crossing the median plane (p. 43). The motor 
paralysis is always of the upper neurone type (p. 3), since the 
cells in the anterior column (cornu) are not involved. 

Complete Transverse Lesions of the spinal medulla neces- 
sarily produce both motor and sensory paralysis. If the lesion 
is placed in the thoracic region, spastic paraplegia results, 
although the paralysed muscles may be flaccid, in the case of 



48 THE NERVOUS SYSTEM 

transverse myelitis, when the disease affects the grey matter in the 
lumbar region. The paralysed limbs are completely anaesthetic 
and there is loss of joint and muscle sense. In most cases, 
since the micturition centre in the hypogastric plexus (p. 373) 
is cut off from its central connexions, there is at first retention 
of urine, but the lower centre soon adapts itself to the altered 
conditions and thereafter the act of micturition becomes 
automatic. 

A complete transverse lesion in the lower cervical region 
produces similar, but more widely spread, sensory and motor 
paralyses. In addition, the symptoms are complicated by 
complete interruption of the connexions between the sym- 
pathetic system and the spinal medulla (p. 186). 

It may sometimes be difficult to determine whether a case 
of spastic paraplegia is functional or organic in origin. If 
the patient is placed in the dorsal decubitus and one limb is 
passively lifted, the position assumed by the opposite limb 
is a valuable guide. When the condition is organic, the 
muscular rigidity causes the pelvis to become tilted, and this 
movement of the pelvis causes the limb to be elevated slightly 
from the bed. 

When the spinal medulla is gradually compressed, e.g. in 
inflammation of the meninges or vertebral caries, motor par- 
alysis is the first sign of nervous complications. As the 
disease progresses, subjective sensory phenomena occur and 
they are accompanied by hyperesthesia. In the later stages, 
there is complete motor and sensory paralysis. 

THE CEREBRAL NERVES 

The First or Olfactory Nerve is represented by a number 
of small branches which arise from the inferior aspect of the 
olfactory bulb. They at once pass downwards through fora- 
mina in the lamina cribrosa of the ethmoid (Fig. 27) and 
gain the interior of the nose, where they are distributed to 
the mucous membrane of the septum and of the lateral wall. 



THE OLFACTORY NERVES 49 

Fractures of the anterior cranial fossa may injure either the 
olfactory bulbs or nerves and give rise to anosmia. The 
olfactory nerves are restricted to the uppermost parts of the 
nasal fossae, and these areas are rarely reached by local 

Foramen 

caecum Crista galli 

Lamina cnbrosa of ethmoid 



/ / 




Position of optic chiasma 

Optic foramen 
, Hypophyseal (pituitary) fossa 
-Superior orbital (sphenoidal) fissure 

Foramen rotundum 

Foramen ovale 
Foramen spinosum 

Internal acoustic meatus 
_. Jugular fcramen 



— Groove for transverse (lateral) 

sinus 
— Mastoid foramen 



Fig. 27. — Floor of Skull. 

anaesthetics. Consequently, although cauterisation of the 
mucous membrane of the inferior meatus of the nose may be 
carried out quite painlessly under local anaesthesia, the patient 
is acutely conscious of the disagreeable odour of the charred 
tissue. 

4 



5° 



THE NERVOUS SYSTEM 



Centrally, the olfactory nerves are connected through the 
olfactory bulb and tract with the fornix and the uncus. Exist- 
ing knowledge is by no means definite with regard to these 
connexions and the symptom of anosmia is of little value, 
therefore, for topical diagnosis. 

The Second or Optic Nerve arises .in the cells of the 
retina and, passing backwards and medially (p. 16), leaves the 



W- 




Retina 



— Optic nerve 



: chiasma 




Optic tract 



\— Tulvinar 



Lateral geniculate body 
Pulvinar 

''^"^""Y-Siiperior corpus quadri- 



geminuni 



Occipital cortex 



FlG. 28. — Diagram of course of Visual and Pupillary Fibres. 

orbit through the optic foramen to reach the optic chiasma 
(Fig. 8). Lesions of the optic nerve will, according to their 
degree of severity, cause partial or complete blindness in the 
eye of the same side. 

The fibres which arise from the nasal side of the retina 
decussate at the optic chiasma and then pass backwards along 
the optic tract of the opposite side. The fibres from the 
temporal side of the retina do not decussate, but enter the 



THE OPTIC NERVE 



5i 



optic tract of the same side. Each optic tract contains, there- 
fore, fibres arising from the temporal half of the retina of its 
own side and fibres arising from the nasal half of the retina 
of the opposite side (Fig. 28). 

The optic tract passes backwards and laterally round the 
lateral side of the cerebral peduncle and its fibres terminate in 
the lower visual centres These consist of — (1) The pulvinar 
of the thalamus (p. 29) ; (2) the lateral geniculate body (p. 
30); and (3) the superior corpora quadrigemina (p. 18). 

Optic tract 

Optic 
nerve 



Lateral geniculate body 

Medial geniculate body 
Pulvinar 



Corpora quadrigemina — 




• Mid-brain 
"orpub mamillare 



-. — Trigeminal nerve 



Pons 
acial nerve 



Fig. 29. — The Lateral Aspect of the Brain-Stem. 

From the cells in the lower visual centres there arise 
new fibres which at once enter the retro-lenticular part of 
the posterior limb of the internal capsule, where they are 
related anteriorly to the acoustic and other sensory fibres. 
They then pass backwards into the occipital lobe and 
terminate in the cortex on its lateral and medial aspects. 
Those fibres which arise in the lower quadrant of the retina 
are connected with the upper portion of the occipital cortex, 
while those from the upper quadrant of the retina are 
connected with the lower portion (p. 13). The lower visual 



52 THE NERVOUS SYSTEM 

centres also establish communications with the nuclei of 
other cerebral nerves. 

Two neurones, therefore, are concerned in the transference 
of stimuli from the retina to the cortex. Lesions which 
affect either the higher neurone or the lower neurone behind 
the optic chiasma produce exactly similar results. The 
temporal half of the homo-lateral retina (nasal side of the 
field of vision) and the nasal half of the hetero-lateral retina 
(temporal side of the field of vision) are both blind. Whether 
the lesion affects the upper or the lower neurone can be de- 
termined by the test for Wernicke's sign. 

Under normal conditions when a strong ray of light 
stimulates the retina, both pupils become contracted. This 
is known as the light reflex, and it is believed that a special 
set of fibres is concerned in its production. These pupillary 
fibres leave the retina in the optic nerve, and at the optic 
chiasma they undergo a decussation which is precisely 
similar to the partial decussation of the visual fibres. They 
then pass backwards in the optic tract, but do not terminate 
in the lower visual centres. Instead, they terminate in the 
iris nucleus^ which is a special collection of cells in the 
nucleus of the oculo-motor nerve. 

In Wernicke's test, a ray of light is reflected on to the 
blind half of the retina and, as the test is extremely delicate, 
great care must be taken to ensure that the light does not 
impinge on the unaffected part of the retina. When the 
upper neurone is the site of the lesion, the light stimulus is not 
interrupted in its passage to the iris nucleus and the light reflex 
is present, so that in this condition Wernicke's sign is positive. 
In affections of the loiver neurone, the pupillary fibres may 
escape when the lesion is situated in the lower visual centres. 
On the other hand, when the lesion involves the optic tract, the 
pupillary fibres are affected to the same extent as the visual 
fibres, and just as the visual stimulus is cut cff from the lower 
centres, causing homonymous hemianopia, so Wernicke's test 
applied to the blind halves of the retinae gives a negative result. 



THE OPTIC NERVE 



53 



Additional signs may be present and may help in the 
localisation of lesions producing homonymous hemianopia. 
Lesions affecting the optic tract are likely to cause some 
motor paralysis or paresis. The third and fourth cerebral 
nerves, owing to their proximity, may be involved, while the 




Fig. 30. — Dissection of Brain, showing the Lateral Aspect of the 

Internal Capsule. 

1. Internal capsule. 6. Optic nerve. 7. Optic tract. 10. Mid-brain. 



lesion may affect the pyramidal tract, as it descends in the 
mid-brain in close relation to the optic tract (Fig. 30). 

When the upper neurone fibres are affected in the internal 
capsule, the adjoining acoustic and sensory fibres (p. 35) are 
likely to be involved, causing the occurrence of deafness and 
of irregularly distributed areas of anaesthesia on the opposite 



54 THE NERVOUS SYSTEM 

side of the body. The condition of quadrantic hemianopia 
in lesions of the occipital cortex has already been described 

(P- 13)- 

The effects which result from pressure on the optic chiasma 
are by no means constant. Homonymous or heteronymous 
hemianopia or complete blindness in one or both eyes may 
occur. Bitemporal hemianopia occurs in many cases of 
acromegaly, and it is due to pressure on the optic chiasma by 
tumours of the hypophysis (pituitary body), which is related 
to its posterior aspect (p. 401). 

The optic chiasma, the posterior ends of the optic nerves, 
and the anterior ends of the optic tracts are all situated in the 
cisterna interpeduncularis (p. in). On this account they are 
often involved in basal meningitis, and the ensuing symptoms 
may be very irregular. 

The "Argyll-Robertson pupil," which is an important early 
symptom of locomotor ataxia, consists in the loss of the light 
reflex, although the pupillary reactions to convergence and 
accommodation remain normal. Since vision is not affected, 
it is not improbable that the condition may be caused by a 
lesion affecting the pupillary fibres, after they leave the optic 
tract and before they reach the iris nucleus (Fig. 28). 

The Third or Oculomotor, the Fourth or Trochlear, 
and the Sixth or Abducent Nerves are all purely motor 
in function, and their distribution is restricted to the muscles 
of the orbit and of the eyeball. 

Note. — It is convenient to describe the course and relations of these 
nerves and to indicate the actions of the orbital muscles, before the distri- 
bution of the nerves and the results of pathological lesions are dealt with. 

The Oculo-niotor Nerve arises from a nucleus which is 
placed in the upper part of the mid-brain in the grey matter 
which surrounds the cerebral aqueduct (Fig. 10). From 
the nucleus the fibres pass forwards through the mid-brain 
and emerge on its anterior surface. The nerve traverses the 
cisterna basalis and pierces the dura mater to the lateral side of 



THE OCULOMOTOR NERVE 



55 



the dorsum sellce of the sphenoid (Fig. 35). The next part of 
its course is situated in the "lateral wall of the cavernous 
sinus (p. 115) between the supporting dura mater and the 
endothelial lining (Fig. 31), where it is closely related to 
the fourth and sixth nerves. It is here placed lateral to the 
hypophysis (pituitary body), but is separated from it by the 
internal carotid artery and the sinus itself. On leaving the 
anterior end of the cavernous sinus, the oculomotor nerve 




Fig. 3r. — Transverse Section through the Cavernous Sinus. 



1. Hypophysis. 

2. Endothelial wall of sinus. 

3. Cavernous sinus. 

4. Internal carotid artery. 

5. Oculo-motor nerve. 

6. Ahducent nerve. 



7. Trochlear nerve. 

8. Serous layer of dura mater. 

9. Ophthalmic nerve. 

10. Sphenoidal air-sinus. 

11. Endo-periosteum of skull. 

12. Maxillary nerve. 



enters the orbit through the superior orbital (sphenoidal) 
fissure. 

The Trochlear Nerve has its nucleus in the lower part 
of the mid-brain. The emerging fibres pass backwards and 
medially from their origin and, crossing the median plane, 
leave the posterior surface of the mid-brain immediately 
below the inferior corpora quadrigemina. The trochlear 
nerve is exceptional, therefore, in two ways : — (1) It arises from 
the dorsal aspect of the brain-stem, and (2) its fibres decussate 
after they leave the nucleus. Thereafter, the nerve winds 



56 



THE NERVOUS SYSTEM 



round the lateral aspect of the mid-brain and enters the 
cisterna basalis. It passes forwards parallel to but below the 
oculo-motor nerve and, after running in the lateral wall of 
the cavernous sinus, enters the orbit through the superior 
orbital fissure. Its relations are practically the same as those 
described for the oculo-motor nerve. 




Fig. 32. — The Posterior Aspect of the Brain-Stem. The left half of the 
Cerebellum has been removed and the right half has been displaced to 
the right side. 



1. Fouith ventricle. 

2. Restiform body. 

^. Medulla oblongata. 



1 4. Clava. 

5. Brachium conjunctivum. 
I 6. Mid-brain. 



7. Brachium pontis. 

8. Superior corpus quadri- 

eeminum. 



The Abducent Nerve arises from a nucleus which is 
situated in the lower part of the pons, immediately under the 
floor of the fourth ventricle (Fig. 23). This nucleus is inti- 
mately related to the fibres of the seventh nerve and, conse- 
quently, lesions of the sixth nucleus are often associated 
with some degree of facial paralysis. From its origin, the 



MUSCLES OF THE ORBIT 57 

sixth nerve passes forwards through the pons and emerges at 
its lower border, near the median plane. Its subsequent 
course is similar to that taken by the third nerve. Having 
crossed the cisterna basalis, it passes through the lateral wall 
of the cavernous sinus and gains the orbit through the superior 
orbital fissure. 

The Muscles of the Orbit. — The levator palpebral superioris 
acts as an elevator of the upper eyelid and is therefore antag- 
onistic to the orbicularis oculi (palpebrarum) (p. 82). When the 
latter muscle is involved in facial paralysis, the increased 
tonus of the unopposed levator keeps the eye constantly open. 
During sleep, however, the levator relaxes and the eye may 
become almost completely closed. The levator palpebral 
superioris is supplied by the third nerve and, when it is 
paralysed, the condition of ptosis results (cf. pseudo-ptosis, 
p. 210). 

The superior rectus passes forwards from the posterior part 
of the orbit and is inserted into the sclerotic coat a little in 
front of the equator. It lies above the eyeball and conse- 
quently acts as an upward rotator. The pull of the superior 
rectus, however, does not impart a pure upward movement 
to the pupil, but it adds a slight medial deviation as well. 

The superior rectus acts in concert with the inferior oblique, 
which arises from the antero-medial part of the floor of the 
orbit and passes laterally and backwards to be inserted into 
the sclerotic behind the equator. It rotates the eyeball so as 
to make the pupil look upwards and laterally. 

When these two muscles act together, they produce a pure 
upward movement, since the medial pull of the superior rectus 
is counterbalanced by the lateral pull of the inferior oblique. 
Both are supplied by the oculo-motor nerve. 

The attachments of the inferior rectus are simliar to those 
of the superior rectus, but the former muscle is applied to 
the inferior aspect of the eyeball so that it acts chiefly as a 
downward rotator. As in the case of the superior rectus, the 



58 THE NERVOUS SYSTEM 

principal movement is complicated by a deviation medially. 
This is counter-balanced by the action of the superior 
oblique, which, acting through a fibrous pulley (Fig. 33), rotates 
the eye so as to make the pupil look downwards and laterally. 
Pure downward rotation is obtained when the two muscles 
act together. The inferior rectus is supplied by the third and 
the superior oblique by the fourth cerebral nerve. 

The lateral and the medial recti are applied, respectively, to 
the lateral and the medial aspects of the eyeball. The former is 
a pure abductor of the eye, i.e., it rotates the eyeball so as to 
make the pupil look laterally. It is supplied by the abducent 
nerve. The medial rectus rotates the eyeball in the opposite 
direction. Its nerve-supply is derived from the oculomotor. 

The intrinsic muscles of the eye are supplied directly from 
the ciliary ganglion (p. 66). The sphincter of the pupil and 
the ciliary muscle (the muscle of accommodation) are inner- 
vated primarily from the oculomotor nerve, while the dilator 
of the pupil gains its supply from the sympathetic system 
(p. 187). 

Paralysis of the Orbital Muscles 

The third, fourth and sixth cerebral nerves are frequently 
all affected by the same lesion, since they follow the same 
intra-cranial course after they emerge from the brainstem, and 
their upper neurones are closely related in the internal capsule, 
the corona radiata and the cortex. 

Supra-nuclear Lesions, unless they are bilateral, rarely 
produce complete paralysis of any of the muscles of the orbit. 
Under normal conditions, the movements of the two eyes are 
always associated. Thus, except in the comparatively rare 
movement of convergence, the lateral rectus always works in 
association with the medial rectus of the opposite side. In 
order that perfect harmony may be obtained, both these 
muscles are bilaterally represented in the cortex. The arrange- 
ment is illustrated in Fig. 20, where it is seen that each 
nucleus receives fibres from the cortex on both sides. Further, 



MUSCLES OF THE ORBIT 



59 




Fig. 33.— The Muscles of the Orbit. 



a. Levator palpebrae superioris, 

divided and turned forward--. 

b. Superior rectus. 

c. Lateral rectus. 

d. Superior oblique. 

e. Orbital periosteum. 



f. Pulley of superior oblique. 

g. Origin of muscles of orbit. 
h. Orbital periosteum. 

i. Medial end of superior orbital 

(sphenoidal) fissure. 
j. Inferior oblique. 



60 THE NERVOUS SYSTEM 

those fibres which come from the same side arise in the group 
of cells which are ultimately connected with the associated 
muscle of the opposite side. 

Nuclear Lesions may be single and they may only involve 
a part of the nucleus. The oculo-motor nucleus contains 
numerous cell-groups, each reserved for one of the muscles 
supplied. On this account, one or more of the muscles inner- 
vated by the oculo-motor may be paralysed in nuclear lesions, 
but paralysis of all the muscles, unless forming part of a crossed 
paralysis — Weber's syndrome (p. 39) — indicates a lesion of 
the trunk of the nerve rather than a lesion of the nucleus. 

The nerves themselves may be affected in purulent effusions 
into the cisterna interpeduncularis (p. in ), or in tumours of the 
interpeduncular fossa or surrounding areas. They may be 
subjected to pressure by tumours of the hypophysis (pituitary 
body) or by aneurisms of the internal carotid artery, as they 
pass forwards in the lateral wall of the cavernous sinus; or by 
tumours or haemorrhages, as they lie in the orbit. 

Results of Paralysis. — Paralysis of the sixth nerve only 
affects the lateral rectus muscle. The loss of movement 
results in the occurrence of a convergent strabismus when the 
patient looks towards the paralysed side. To overcome this 
disability, the patient tends to keep his head rotated to the 
side of the lesion, thus obviating the necessity for lateral 
rotation of the affected eye. 

When the fourth nerve is involved by itself, the superior 
oblique is the only muscle which is paralysed. Under these 
circumstances, the eye deviates to the medial side when down- 
ward rotation is attempted, since the medial pull of the inferior 
rectus is no longer counter-balanced by the lateral pull of the 
superior oblique. The other movements of the eye are not 
affected, and disability is only noticed by the patient when he 
has to look downwards, e.g., in going downstairs ; he then suffers 
from diplo-opia. 

In complete paralysis of the third nerve the eye only retains 
those movements which are due to the superior oblique and 



THE TRIGEMINAL NERVE 61 

the lateral rectus. When at rest, the paralysed eye looks 
downwards and laterally, and the patient, therefore, tends to 
walk with the head rotated to the opposite side so as to enable 
him to look directly forwards. In addition to the disability pro- 
duced by the paralysis of the ocular muscles, ptosis results 
owing to paralysis of the levator palpebral superioris. In an 
endeavour to counteract this condition, the patient extends the 
head on the trunk and actively contracts the frontalis muscle. 

Owing to the paralysis of the sphincter pupillre, the pupil is 
widely dilated by the unopposed dilator muscle (p. 67). The 
ciliary muscle is also affected and, therefore, the accommoda- 
tion reflex is lost in addition to the light reflex. 

The Fifth or Trigeminal Nerve contains both motor and 
sensory fibres, and it therefore possesses two nuclei. The 
Motor Nucleus is an elongated mass of grey matter, which 
lies in the upper half of the pons ; further, some cells which lie 
in the grey matter around the cerebral aqueduct (of Sylvius) in 
the mid-brain send their fibres down to join the motor root of 
the tri<reminal. The nucleus receives fibres from the cortex 
of both cerebral hemispheres, and, therefore, supra-nuclear 
lesions do not cause complete paralysis of the muscles supplied 
on the opposite side of the body. Nuclear lesions are accom- 
panied by complete paralysis of the muscles of mastication 
(p. 70) on the same side as the lesion ; they sometimes occur 
late in the course of bulbar paralysis (p. 108). 

The Sensory Nucleus is placed in the lower half of the 
pons, and extends downwards through the whole length of the 
medulla oblongata into the spinal medulla, in which it reaches 
the level of the second cervical segment. In the pons, it lies 
postero-lateral to the nucleus of the facial nerve and lateral to 
the ascending sensory fibres (spinothalamic tract) from the 
spinal medulla (Fig. 34). A nuclear lesion, therefore, not only 
causes anaesthesia in the area of distribution of the trigeminal, 
but it may also cause partial or complete anaesthesia of the 
limbs and trunk on the opposite side, owing to involvement 



62 



THE NERVOUS SYSTEM 



of the spinothalamic tract. The condition is termed alternate 
hemi-ancesthesia, and it may or may not be accompanied by 
homo-lateral facial paralysis (p. 86). 

The small motor and the large sensory roots emerge side by 
side from the lateral part of the pons near its upper border, 
and run laterally through the subarachnoid space before they 
pierce the dura mater at the apex of the 'petrous part of the 
temporal bone (Fig. 35). The acoustic (auditory) nerve, as 




■ Facia! 
rr""" nerve 



"* Motor fibres 
Fig. 34. — Transverse Section through the Pons (Diagrammatic). 



it passes from the internal acoustic meatus to the pons, lies a 
little below the trigeminal. Paralysis of the fifth, with signs 
of cerebellar disease, and with or without symptoms of deaf- 
ness, is diagnostic of tumour in the neighbourhood of the 
cerebellopontine angle (p. 22). 

The Semilunar (Gasserian) Ganglion, which corre- 
sponds to the ganglion on the posterior root of a spinal 
nerve, is placed on the sensory root of the trigeminal as it lies 
on the anterior part of the petrous temporal. It lies immedi- 
ately postero-lateral to the cavernous sinus and receives 



THE TRIGEMINAL NERVE 



63 



branches from the cervical sympathetic, which enter the skull 
in company with the internal carotid artery (p. 186). These 
branches are destined to supply the dilator muscle of the iris. 




FlG. 35. — Interior of the Skull after the removal of the Brain, showing the 
points of exit of the twelve cerebral nerves. 

The small motor root takes no part in the formation of the 
semilunar ganglion. Since it lies between the ganglion and 
the bone, it can be left behind uninjured when the ganglion is 



6 4 



THE NERVOUS SYSTEM 



removed. The ophthalmic, maxillary and mandibular (inferior 
maxillary) nerves arise from the anterior border of the semi- 




4 2 5 

Fig. 36. — The Branches of the Ophthalmic Nerve. 



a. 


Roof of orbit. 






4- 


J'rigeminal nerve. 


b. 


Crista galli. 






5- 


Ophthalmic nerve. 


c. 


Dorsum sella;. 






6. 


Lacrimal nerve. 


d. 


Petrous temporal. 






7- 


Trochlear nerve. 


e. 


Cut edge of skull. 






8. 


Infra-trochlear nerve. 


f. 


Orbicularis oculi muscle. 




9- 


Anterior ethmoidal nerve. 


& m 


Superior oblique muscle. 




10. 


Frontal nerve. 


h. 


Levator palpebra; s 


jperions. 




11. 


Supra-orbital nerve (lateral branch). 


k. 


Superior rectus mus 


cle. 




12. 


Supra-orbital nerve (medial branch) 


1. 


Lacrimal gland. 






13- 


Supra-trochlear nerve. 


111. 


Eye-ball. 






14- 


Semilunar (Gasserian) ganglion. 


1. 


Optic nerve. 






IS- 


Oculo-motor nerve. 


2. 


Oculo-motor nerve. 






16. 


Trochlear nerve. 




Trochlear nerve. 






17- 


Branch to tentorium cerebelli. 






18. 


Abdu 


:ent nerve. 



lunar ganglion, and the last-named is joined by the whole of 
the small motor root. 

1. The Ophthalmic Nerve, which is purely sensory, arises 
from the semilunar ganglion, and at once enters the lateral wall 



THE TRIGEMINAL NERVE 65 

of the cavernous sinus, where it is related to the third, fourth 
and sixth cerebral nerves, the internal carotid artery, and 
the hypophysis (pituitary body) (Fig. 31). At the anterior 
extremity of the sinus, it enters the orbit through the superior 
orbital (sphenoidal) fissure and breaks up into its terminal 
branches. 

(a) The Frontal Nerve passes forwards in contact with 
the roof of the orbit and divides into the supra-orbital and the 
supra-trochlear nerves. The supra-orbital passes forwards and 
leaves the orbit through the supra-orbital notch, which may be 
felt on the upper border of the base of the orbit (orbital aper- 
ture) at a distance of two fingers'-breadth from the median 
plane. It then turns upwards and supplies a wide area of the 
skin of the forehead and scalp, extending as far back as the 
vertex (Fig. 37). In addition, the supra-orbital nerve supplies 
the skin and the underlying conjunctiva of rather more than 
the middle third of the upper eyelid. The sympathetic fibres 
which supply the ciliary bundle (p. 210) are probably carried 
by the supra-orbital nerve. 

The supra-trochlear is a much smaller nerve, which supplies 
the skin and conjunctiva of the medial part of the upper eyelid 
and gives a few twigs to the skin of the forehead just above the 
root of the nose (Fig. 37). 

{b) The Lacrimal Nerve passes forwards along the upper 
border of the lateral rectus muscle and receives a communicat- 
ing branch from the zygomatic (orbital) nerve, which conveys 
the secreto-motor fibres (p. 69) for the lacrimal gland. After 
supplying the gland (p. 208), the nerve is distributed to the 
skin and conjunctiva of the lateral part of the upper eyelid 

(Fig- 37)- 

(c) The Naso-ciliary (Nasal) Nerve runs forwards across 
the optic nerve to the medial wall of the orbit. It gives off 
the long root to the ciliary ganglion and the long ciliary nerves, 
which pass forwards to the coats of the eyeball. In addition, 
it supplies the skin in the region of the medial canthus by 
means of the infra-trochlear nerve. The terminal branch of 
5 



66 



THE NERVOUS SYSTEM 



the nasociliary nerve eventually reaches the nasal fossa and 
supplies branches to the mucous membrane of the septum and 
lateral wall. Finally, it emerges on the face and is distributed 



Supra-orbital n^rve- 



Auriculo-temporal nerve- 

Zygomatico-temporal nerve - 

Supra-trochlear nerve - 

Lacrimal nerve 

Infra-trochlear nerve ■ 

Zygomaticofacial nerve • 

Infra-orbital nerve 

External nasal nerve ■ 

Buccinator nerve - 



Mental nerve — 




Fig. 37. — The Cutaneous Branches of the Trigeminal Nerve. 

to the skin of the anterior part of the side of the nose 

( Fi g- 37). 

The Ciliary Ganglion lies in the orbital fat between the 
optic nerve and the lateral rectus muscle. It receives a short 
motor root from the oculomotor, destined for the sphincter 
iridis and the ciliary muscle (p. 213), and a long root from the 
naso-ciliary nerve. The long root conveys some of the sym- 



THE TRIGEMINAL NERVE 



67 



pathetic fibres which join the semilunar (Gasserian) ganglion, 
and they are destined for the dilatator iridis. The ciliary 
ganglion contains some nerve-cells which form a peripheral 
controlling centre for the light reflex. Degenerative changes 
have been found in the ganglion in cases showing a typical 




Fig. 38. — The Branches of the Maxillary Nerve. 



1. Semilunar (Gasserian) ganglion. 

2. Ophthalmic nerve. 

3. Maxillary nerve. 

4. Zygomatic nerve. 

5. I'ranch communicating with lacri- 

mal nerve. 

6. Zygomaticofacial nerve. 

7. Zygomaticotemporal nerve. 



8. Spheno-palatine ganglion (of Meckel). 

g. Nerve of pterygoid canal (Vidian). 
10. Greater superficial petrosal nerve, 
n. Facial nerve. 

12. Deep petrosal nerve. 

13. Palatine nerves. 

14. Posterior superior alveolar (dental) 

nerve. 



15. Infra-orbital nerve. 

"Argyll-Robertson pupil" (p. 54). The short ciliary nerves 
arise from the ganglion and proceed forwards to the eyeball. 

The various pathological conditions affecting the ophthalmic 
nerve are indicated on page 77. 

2. The Maxillary Nerve is, like the ophthalmic, a purely 
sensory nerve. From the semilunar (Gasserian) ganglion 
it runs forwards on the floor of the middle cranial fossa, 



68 THE NERVOUS SYSTEM 

lateral to the cavernous sinus, and passes through the fora- 
men rotundum in the great wing of the sphenoid (Fig. 35). It 
then runs obliquely across the uppermost part of the pterygo- 
palatine (spheno-maxillary) fossa and enters the orbit through 
the inferior orbital (spheno-maxillary) fissure (Fig. 38). 

In this part of its course the maxillary nerve can be reached 
with a hypodermic needle for the purpose of injecting absolute 
alcohol, or some other destructive agents, into and around it. 
The needle is entered immediately below the zygomatic arch 
at a point 4 cms. in front of the anterior wall of the external 
acoustic meatus (Symington). The nerve lies at a depth of 
5 ,cms. from the surface, but it is probable that, before it 
reaches this depth, the needle will impinge either on the 
posterior part of the maxilla or on the lateral pterygoid lamina 
(Fig. 38). It will require to be withdrawn partially and 
re-inserted until it passes through the pterygo-maxillary fissure 
and enters the pterygo-palatine (spheno-maxillary) fossa. The 
contents of the syringe can then be injected around the 
maxillary nerve. 

As the maxillary nerve lies in the pterygo-palatine fossa, it 
is connected to the spheno-palatine (Meckel's) ganglion by 
two roots (Fig. 38). 

The Spheno-Palatine Ganglion receives additional 
afferent fibres from the nervus canalis pterygoidei (Vidian 
nerve), which is formed by the union of the greater superficial 
petrosal nerve from the facial with the deep petrosal nerve 
from the cervical sympathetic. Branches arise from the 
ganglion and are distributed to the mucous membrane (1) 
of the lateral walls and septum of the nose, (2) of the hard- 
palate and gums, (3) of the soft palate and the palatine 
(faucial) tonsil, and (4) of the roof of the nasal part of the 
pharynx. 

It is possible that the spheno-palatine ganglion takes part 
in the innervation of the muscles of the soft palate, but this 
view is not generally accepted (p. 96). 

In the orbit, the maxillary nerve gives off the zygomatic 



THE TRIGEMINAL NERVE 69 

(orbital) nerve, which communicates with the lacrimal (p. 65) 
and emerges as two small branches to supply the skin of the 
face behind the eye (Fig. 37). The communicating branch 
conveys to the lacrimal the secreto-motor fibres for the 
lacrimal gland. These fibres probably emerge from the 
brain-stem with the facial nerve, and pass by the greater 
superficial petrosal to the spheno-palatine ganglion and the 
maxillary nerve. 

In this situation, also, the maxillary gives off the posterior 
superior alveolar (dental) nerve, which is distributed to the 
molar teeth of the maxilla. It then enters the infra-orbital 
canal in the floor of the orbit (Fig. 38) and supplies the 
remaining maxillary teeth by means of the middle and the 
anterior alveolar branches. Finally, the maxillary nerve 
emerges from the infra-orbital foramen as the infra-orbital 
nerve and appears on the face. 

The infra-orbital nerve breaks up into a large number of 
branches. They supply — (1) The skin and conjunctiva of 
the lower eyelid; (2) the skin on the postero-lateral aspect of 
the nose ; (3) the skin and mucous membrane of the upper lip ; 
(4) the skin and mucous membrane of the cheek. In addition, 
the infra-orbital nerve supplies sensory fibres to a large 
number of the facial muscles (p. 84). 

3. The Mandibular Nerve carries off the whole of the 
motor root of the trigeminal and, in addition, it contains a 
large number of sensory fibres. It arises from the lateral 
part of the semilunar ganglion, and leaves the interior 
of the skull by passing downwards through the fora- 
men ovale (Fig. 35). This course brings it at once into 
the region of the pterygoid muscles, and, immediately below 
the skull, the nerve lies between the external pterygoid, on the 
lateral side, and the lateral wall of the naso-pharynx, on the 
medial side. 

Corrosive fluids may be injected around the nerve in this 
part of its course, and they will affect it above the point where 
the important sensory branches arise. The mouth is held 



70 THE NERVOUS SYSTEM 

open, preferably by a gag, so as to tilt the coronoid process 
forwards, and the needle is entered below the posterior part 
of the zygomatic arch and immediately in front of the 
temporo-mandibular joint (Fig. 39). It is passed medially and 
slightly backwards for a distance of 4 cms. from the surface, 
and the contents of the syringe may then be injected 
(Symington). The masseter, temporal and both pterygoid 
muscles are pierced in turn, and their bulk accounts for the 
depth to which the needle must be thrust. As in the case 
of the maxillary nerve, it is advisable to perform the operation 
without an anaesthetic, as the severe pain caused by the 
entrance of the point of the needle into the nerve is the surest 
guide to the site of injection. Care must be taken not to pass 
the needle in too far, as it may pierce the lateral wall of the 
naso-pharynx or the terminal part of the auditory (Eustachian) 
tube (p. 329). 

The Otic Ganglion is connected with the mandibular 
nerve immediately below the foramen ovale. It receives 
fibres not only from the trigeminal but also, through the lesser 
superficial petrosal nerve (p. 92), from the facial and the 
glosso-pharyngeal nerves. The efferent fibres are partly 
secretory and partly motor. The secretory fibres join the 
auriculotemporal nerve, and are conveyed by it to the 
parotid gland ; the motor fibres supply the tensor tympani 
(p. 204) and the tensor veli palatini (tensor palati). It is not 
yet certain whether the motor fibres originate in the motor 
nucleus of the fifth or the seventh. 

The mandibular nerve is responsible for the innervation 
of the Muscles of Mastication. They include the temporal, 
the masseter, the internal pterygoid, the external pterygoid, the 
mylo-hyoid and the anterior belly of the digastric. 

The Temporal and the Masseter muscles elevate the 
mandible and are rendered tense when the teeth are firmly 
clenched. The contractions of the temporal muscle can be 
appreciated best near its upper border, about 2 inches or 



7 
2 

1 

10 

8 




15 

Fig. 39. — The Branches of the Mandibular Nerve. The zygomatic 
arch and a portion of the ramus of the mandible have been removed. 
In addition, the lower part of the temporal muscle has been resected 
and the masseter has been turned downwards. 

Deep temporal nerve. 
Auriculotemporal nerve. 
Temporal fascia. 
Mastoid process. 
Facial nerve. 
Lingual nerve. 
Roots of teeth. 
Mental branch of inferior 
alveolar (dental) nerve. 
6. Lateral pterygoid lamina. 



b. 


External pterygoid muscle. 


7- 


c. 


Internal pterygoid muscle. 


8. 


d. 


Masseter muscle. 


9- 


e. 


Buccinator muscle. 


10. 


1. 


Masseteric nerve. 


1 1. 


2. 


Temporomandibular joint. 


12. 


3- 


Buccinator nerve. 


14- 


4- 


Maxilla. 


15- 


5- 


Branch to temporal muscle. 





72 THE NERVOUS SYSTEM 

more above the zygomatic arch. At a lower level, the 
temporal fascia is so strong and dense that the contractions 
of the muscle cannot be felt. The contractions of the 
masseter can be felt in the posterior part of the side of the 
face, below the zygomatic arch. 

The Pterygoid Muscles arise in the region of the 
pterygoid process of the sphenoid, and pass backwards and 
laterally to be inserted into the mandible. They therefore 
protrude the mandible and move it from side to side. They 
are deeply situated under cover of the mandibular ramus, 
and their contractions cannot be examined satisfactorily. 
When the pterygoid muscles of one side act in unison, that 
half of the mandible is drawn towards the median plane, and 
the opposite half is consequently thrust in a lateral direction. 
No other muscles assist the pterygoids in producing side to 
side movements. 

The Mylo - hyoid and the Anterior Belly of the 
Digastric act as depressors of the mandible. The former 
extends from the mylo-hyoid line on the inner surface of the 
body of the mandible to the body of the hyoid bone. The 
anterior fibres of the two mylo hyoids are inserted into a 
median raphe, which extends from the symphysis menti to the 
middle of the hyoid bone, and together they form a muscular 
floor for the mouth. In addition to their action as depressors 
of the mandible, the mylo-hyoids act as elevators of the hyoid 
bone, when the mandible is fixed, e.g. in swallowing (p. 229), 
and they steady the hyoid during the movements of the 
tongue. 

In the median plane, between the chin and the hyoid bone, 
the mylo-hyoid is covered only by the skin and fascia; and 
its contractions can be palpated in this situation. They are 
felt most readily when the tongue is pressed against the hard 
palate. Unfortunately, the genio-hyoid (p. 106) is rendered 
tense by the same action and, in consequence, paralysis of 
the mylo-hyoid is very difficult to determine. 

The anterior belly of the digastric is probably more efficient 



THE TRIGEMINAL NERVE 73 

as an elevator of the hyoid bone than as a depressor of the 
mandible. The posterior belly (facial nerve, p. 81) arises 
on the medial side of the base of the mastoid process and 
passes forwards and downwards, deep to the angle of the 
mandible, to the greater cornu of the hyoid bone. It 
terminates in the common tendon of the muscle, which is 
attached to the greater cornu by a slip of the deep cervical 
fascia. The anterior belly passes forwards and medially 
from the common tendon to be attached to the base of the 
mandible near the median plane. It is placed superficial to 
the mylo-hyoid, but is partially overlapped by the submaxillary 
salivary gland. 

Paralysis of the motor part of the trigeminal is usually 
accompanied by some involvement of the sensory fibres. 
Owing to bilateral representation in the cerebral cortex (p. 
34), the muscles of mastication are rarely affected in lesions 
of the internal capsule or the corona radiata. 

Nuclear lesions have already been referred to (p. 61). 

The motor root of the fifth, as it lies on the apex of the 
petrous part of the temporal bone, may be affected in 
syphilitic basal meningitis, and, in these cases, the whole of 
the sensory distribution of the trigeminal will be involved, 
probably together with the third and fourth cerebral nerves. 

The motor root may be affected in extra-cranial tumours 
which compress the mandibular nerve. 

In complete motor paralysis of the trigeminal the principal 
disability is caused by the lack of opposition to the pterygoid 
muscles of the sound side. The unparalysed elevators and 
depressors are sufficiently powerful to carry out their respective 
movements, but the tonus of the unopposed pterygoids causes 
the jaw to be thrust over to the paralysed side, and so the 
teeth do not oppose one another in a satisfactory manner 
during mastication. 

Some authorities state that the free border of the soft 
palate lies at a lower level on the paralysed side, but others 
have failed to observe any affection either of the soft palate 



/ 



74 



THE NERVOUS SYSTEM 



or of the sense of hearing (tensor veli palatini and tensor 
tympani, p. 204). 

Four large sensory branches arise from the mandibular 
nerve immediately below the foramen ovale. 



Supra-orbital naive 



Auriculotemporal 

Zygomatico- temporal 

Supra-trochlear 

Lacrimal 

Infra-trochleai 

Zygomatico-facia 

Infra-orbital 

External nasa 

Buccinator 



Mental nerve 




Fig. 40. — The Cutaneous Branches of the Trigeminal Nerve. 



i. The Auriculo-temporal Nerve receives a communicating 
branch from the otic ganglion (p. 70) and passes backwards 
under cover of the neck of the mandible. It then enters the 
parotid gland and, after supplying it with secretory fibres, 
ascends over the zygomatic arch immediately in front of the 



THE TRIGEMINAL NERVE 75 

external ear. The full distribution of the nerve includes a 
strip of skin on the side of the head (Fig. 40), the skin of 
the upper and anterior part of the external ear, and the skin 
which lines the external acoustic meatus and the lateral 
aspect of the tympanic membrane. 

2. The Buccinator (Long Buccal) Nerve supplies the skin 
of the cheek behind the area innervated by the infra-orbital 
nerve (Fig. 40). Many of its branches pierce the substance 
of the cheek and supply the mucous membrane. When the 
buccinator nerve is paralysed, portions of food tend to remain 
lodged in the grooves between the cheek and the gums. 
This is due to anaesthesia of the mucous membrane and not 
to paralysis of the buccinator muscle, which is supplied by 
the facial nerve (p. 82). 

3. The Inferior Alveolar (Dental) Nerve enters the 
mandibular canal and supplies all the teeth of the lower 
jaw. Its terminal branch, termed the mental nerve, emerges 
on the outer surface of the mandible through the mental 
foramen and supplies the skin of the lower lip, the chin and 
adjoining areas and the mucous membrane of the lower lip 
(Fig. 40). 

4. The Lingual Nerve descends under cover of the ramus 
of the mandible and passes forwards deep to the body of the 
bone to enter the submaxillary region and reach the tongue 
(Fig. 49). It supplies the mucous membrane of the floor of 
the mouth and the anterior two-thirds of the tongue with 
ordinary sensation. When a spatula is introduced into the 
mouth, no unpleasant sensations are aroused as long as the 
instrument is in contact with the area supplied by the 
lingual nerve, but if it touches the posterior third — or the 
posterior part of the middle third, for the nerves supplying 
adjoining areas overlap one another in their distribution — 
the glossopharyngeal nerve is stimulated and the pharyngeal 
reflex is set up. 

In the first part of its course, the lingual nerve is joined by 
the chorda tympani (p. 84), through which it supplies taste 



76 THE NERVOUS SYSTEM 

fibres to the anterior two-thirds of the tongue. The course of 
the taste fibres is discussed on page 84. 

The Submaxillary Ganglion is connected with the lingual 
nerve, as it lies on the side of the tongue. The afferent 




Fig. 41. — The Areas of Skin supplied by the three divisions 
of the Trigeminal Nerve. 

fibres from the nerve to the ganglion are derived from the 
chorda tympani (p. 84). They are the secretory nerves for 
the submaxillary and sublingual salivary glands, to which 
they are distributed. 



THE TRIGEMINAL NERVE 



// 



In Fig. 41 the areas of distribution of the three great 
divisions of the trigeminal have been indicated schematically. 
It will be observed that the trigeminal is responsible for the 
supply of the skin of the whole of the face with the exception 
of a small area over the angle of the mandible, which is 
supplied by the great auricular nerve (C. 2 and 3). In 
addition, it supplies the skin of the anterior part of the head, 
the upper part of the external ear and the skin lining the 
external acoustic meatus. 

The sensory branches of the fifth also supply a wide area of 
mucous membrane, including the conjunctival sacs, the nose, 
cheeks, lips, gums, palate, floor of the mouth and anterior 
two-thirds of the tongue. 



'£>* 



Paralysis of the Sensory Part of the 
Trigeminal Nerve 

Lesions of the sensory nucleus are usually associated with 
the condition of alternate hemi-anaesthesia (p. 62). 

Complete unilateral anaesthesia in the region supplied by 
the fifth nerve, unaccompanied by anaesthesia in other 
regions, indicates a lesion of the large sensory root or the 
semilunar (Gasserian) ganglion, usually caused by an intra- 
cranial tumour in the cerebello-pontine angle. The cutaneous 
anaesthesia reaches exactly to the median plane, as the two 
trigeminal nerves do not overlap one another. As a result, 
when the patient drinks from a vessel, it feels to him as if it 
were broken, since the part in contact with the anaesthetic 
halves of the lips cannot be appreciated. 

Trigeminal paralysis also produces marked effects on the 
areas of mucous membrane which are rendered anaesthetic. 
The mucous membranes of the nose, cheeks and tongue 
become dry, and atrophic changes may occur. Ulceration of 
the cornea is not uncommon. 

Trigeminal Neuralgia. — Conditions which give rise to pain 
in the areas supplied by the trigeminal may be immedi- 
ately or only remotely connected with the nerve itself. 



78 THE NERVOUS SYSTEM 

The lesion in tic douloureux is not definitely known, but 
it presumably affects either the semilunar (Gasserian) ganglion 
or the sensory root of the nerve. In this case the pain 
starts in one particular branch and, later, spreads to affect 
other branches of the same division. It is important to 
observe that the pain is restricted to the areas of peripheral 
distribution (Fig. 41). After a time, hyperresthetic areas 
develop in the skin of the face or head, and their appearance 
is due to the establishment of a "focus of irritation" (p. 195) 
in the sensory nucleus of V. 

Pain of a similar nature may be caused by an intracranial 
tumour in its early stages. 

Referred pain (p. 190) occurs in the trigeminal area with 
great frequency. Head has pointed out that two distinct 
varieties of referred pain occur in this area. In one the pain 
is radiating or neuralgic in type and affects the area of 
distribution of a definite branch or branches of the trigeminal. 
Pyorrhcea alveolaris gives rise to such a condition and may 
be accompanied by the development of localised areas of 
hyperesthesia, which are restricted to the same regions. 

In the other variety, the pain does not radiate and is 
constantly referred to a definite area, which does not corre- 
spond to the peripheral distribution of any one branch of 
the fifth. Hyperaesthetic areas may develop, and they are 
localised to the same " segmental " regions. This variety 
of referred pain is met with in iritis, glaucoma and inflamma- 
tion of the tooth pulp. The lower molars are intimately 
related to the skin over the posterior part of the ramus of 
the mandible and to the skin lining the external acoustic 
meatus. In irritation of the pulp of a lower molar, there 
may be no local pain and yet the ear pain may be very acute. 
These cases may readily lead to wrong diagnosis. 1 

When a "focus of irritation" (p. 195) is established in the 

1 For a full description of the "segmental" areas and their relation to 
the teeth, the reader is referred to Head's article in Allbutt and Rolleston's 
System of Medicine. 



THE TRIGEMINAL NERVE 



79 



sensory nucleus of the trigeminal, it may spread to affect the 
neighbouring grey matter. As a result, pain may be ex- 
perienced, or hyper?esthetic areas may develop, on the side 
of the neck in areas supplied by C. 2 and 3 (Fig. 69). 

It must also be remembered that, when a "focus of 
irritation " is established in a sensory nucleus which is related 
to the sensory nucleus of the trigeminal, the latter may also 
be stimulated. This explanation accounts for the occurrence 







Facial 
nerve 



Motor fibres 
Fig. 42. — Transverse Section through the Pons (Diagrammatic). 



of pain in the head or face in lesions of the lungs, heart or 
stomach. The pathological afferent impulses set up a " focus 
of irritation " in the sensory nucleus of the vagus, and from 
there they spread to affect the sensory nucleus of the fifth 
(Fig. 47)- 



The Facial or Seventh Cerebral Nerve consists of a 
large motor root and a small sensory root which is termed the 
tiervus intermedins {of Wrisberg) The motor root arises in 
a nucleus, which is situated in the substance of the pons, 



8o THE NERVOUS SYSTEM 

dorsal to the bundles of the pyramidal tract and medial 
to the sensory nucleus of the trigeminal (Fig. 42). After 
they leave the nucleus, the efferent fibres pass backwards 
and curl round the nucleus of the sixth nerve, at the 
same time forming an elevation in the floor of the fourth 
ventricle (p. 56). They then turn forwards and pass through 
the whole substance of the pons, finally emerging near its 
lower border (Fig. 8). 

The motor part of the facial, the nervus intermedius, and 
the eighth nerve pass laterally together through the sub- 
arachnoid space and enter the petrous part of the temporal 
bone through the internal acoustic meatus. 

At the bottom of the internal acoustic meatus, the facial 
and the nervus intermedius enter a small canal, in which 
they pass laterally to the medial wall of the tympanic cavity. 
At this point the canal bends sharply backwards, and a 
small swelling, termed the geniculate ganglion, is situated 
on the facial nerve. It is from this ganglion that the nervus 
intermedius arises. The course taken by the sensory fibres 
of the seventh is described on page 84. 

As the facial canal passes backwards along the medial 
wall of the tympanum, the facial nerve is separated from 
the middle ear only by a thin plate of bone, which may 
readily become necrosed in otitis media. Opposite the aditus 
to the tympanic (mastoid) antrum (p. 206), the nerve makes 
a second bend, this time in a downward direction, and 
reaches the stylo-mastoid foramen on the inferior surface of 
the skull. As it descends in the last stage of its passage 
through the temporal bone, the facial nerve is joined by the 
chorda tympani and it gives off the nerve of supply to the 
stapedius muscle. 

The stapedius muscle arises within the posterior wall of the 
tympanic cavity and passes forwards to be inserted into the 
neck of the stapes (p. 205). It would appear to act as an 
antagonist of the tensor tympani, for the condition of 
hyperacousis results when the stapedius is paralysed. In this 



THE FACIAL NERVE 



Si 



condition, certain sounds become greatly exaggerated and 
the patient may even complain that they cause definite pain. 
The stapedius is not paralysed in supra-nuclear lesions of 
the facial, and it is, therefore, believed that it possesses 
bilateral representation in the cerebral cortex. 

The course of the chorda tympani is described on page 84. 

It is sometimes desirable to apply a counter-irritant over 




Fig. 43. — -Schematic representation of the Branches of the Facial Nerve. 



1 Facial nerve. 

2. Nervus intermedius (of Wrisberg). 

3. Acoustic nerve. 

4. Greater superficial petrosal nerve. 

5. Geniculate ganglion. 

6. Nerve to stapedius. 

7. Stylo-mastoid foramen. 



8. Posterior auricular nerve. 

g. Nerve to stylo-hyoid and posterior 

belly of digastric. 
10 Chorda tympani. 

1 1. Lingual nerve 

12. Terminal branches of facial 

nerve. 



the facial nerve at the point where it emerges from the stylo- 
mastoid foramen. This point corresponds on the surface to 
the upper part of the depression between the mastoid process 
and the external ear. 

After leaving the skull, the facial nerve gives off certain 

muscular branches, before it enters the parotid gland. These 

branches are distributed to the occipitalis, the posterior and 

superior auricular muscles, and the posterior belly of the digastric 

6 



82 THE NERVOUS SYSTEM 

and the stylo-hyoid. No description of the actions, etc., of 
these muscles is necessary, as their investigation is rarely 
called for in cases of facial paralysis. 

/;/ the parotid gland the facial nerve passes forwards across 
the lateral aspect of the neck of the mandible, and, in this 
situation, it is exposed to injury, e.g. by the application of 
forceps during delivery. As the fascial sheath of the gland 
is so strong that even a slight enlargement of the parotid may 
be sufficient to exert pressure on the nerve, facial paralysis 
may be a complication of acute parotitis. 

The terminal branches of the facial nerve arise within the 
parotid gland and they supply all the muscles of facial 
expression, including the buccinator, the platysma and the 
frontalis. 

Peripheral Lesions of the Facial Nerve. — In complete 
facial paralysis, due to a lesion outside the skull, all the 
muscles of expression are completely paralysed. As a result, 
the affected side of the face is immobile and the natural skin 
creases disappear. 

The Orbicularis Oculi (Palpebrarum) lies partly in the eye- 
lids and partly around the margins of the base (external 
aperture) of the orbit. It acts as a sphincter of the eyelids 
and its tonus serves to keep the puncta lacrimalia closely 
applied to the surface of the eye (p. 210). When this muscle 
is paralysed, the eye remains open and attempts to close it 
result only in upward rotation of the eyeball. The con- 
junctival reflex is therefore abolished, but automatic winking 
does not cease and the eye may become closed during sleep. 
These two latter movements are due to relaxation of the 
levator palpebral superioris. In addition, paralysis of the 
orbicularis oculi is accompanied by the condition of epiphora 
(p. 210). 

The Buccinator forms the muscular stratum of the cheek. 
Its fibres arise from the inner alveolar borders of the 
mandible and maxilla, opposite the molar teeth, and also 
from a ligamentous band, termed the pterygo-mandibular 




P r-K 



Pig. 44. — The Facial Nerve and its Ramifications. 



a. Frontalis muscle. 

b. Occipitalis muscle, 
c, d, c. Auricular muscles. 

y. Orbicularis oculi muscle. 
g. Quadratus labii superior muscle. 
h. Buccinator muscle. 
k. Masseter muscle. 
/. Parotid gland. 
in. Laryngeal prominence. 
n. Digastric muscle, posterior belly. 

0. Sterno-mastoid muscle. 
/. Trapezius muscle. 

1. Facial nerve. 

2. Posterior auricular nerve. 

3. Mastoid process. 

4. Nerve to occipitalis muscle. 



5. 6. Nerves to auricular muscles. 

7. Communication between facial and 

great auricular nerves. 

8. Nerve to stylo-hyoid. 

9. Temporo-facial division. 
10-14. Temporal branches. 

15. Zygomatic branches. 
r6. Infra-orbital nerve. 
18. Cervico-facial division. 
19, 20. Buccal branches. 

2r. Mandibular branches. 

22. Mental nerve. 

23. Cervical branch. 

24. Nervus cutaneus colli. 

25. Parotid branches of auriculo- 

temporal nerve. 



84 THE NERVOUS SYSTEM 

raphe. They pass horizontally forwards and blend with the 
orbicularis oris at the angle of the mouth. When the 
buccinator contracts, it draws the angle of the mouth back- 
wards, but, if the angle of the mouth is fixed, e.g. by the 
contraction of the orbicularis oris, it compresses the cheek 
against the gum. This latter action can readily be tested if 
the finger is placed in the groove between the gum and the 
cheek. In paralysis of the buccinator, as also in trigeminal 
paralysis (p. 75), portions of food tend to remain lodged in 
this groove and, by decomposition, they impart a foul odour 
to the breath. Further, the unopposed buccinator of the 
sound side draws the mouth over to that side, and this de- 
formity is very characteristic of all varieties of facial palsy. 

The Orbicularis Oris forms a sphincter muscle for the 
mouth. It is called into action in closing the mouth and it 
purses the lips in whistling and sucking. Other muscles, 
which need not be detailed, aid the orbicularis in movements 
of the lips. Paralysis of these muscles not only results in the 
dribbling of fluids, saliva, etc., from the mouth, but also 
renders the pronunciation of labials and labio-dentals (3, c, f, 
m, />, and r) slurred and indistinct. 

Before the results of intra-cranial lesions of the facial nerve 
are described, it is necessary to refer to the path of the taste 
fibres and the functions of the chorda tympani. 

The Chorda Tympani contains both afferent and efferent 
fibres. The nerve begins in the descending part of the facial 
canal and passes forwards into the tympanum. It crosses the 
deep surface of the tympanic membrane near its upper border 
(p. 202) and then runs through a small bony canal to gain 
the infra-temporal fossa (pterygo-maxillary region), where it 
joins the lingual nerve. 

It contains the taste fibres from the anterior two-thirds of 
the tongue and the secretory fibres for the submaxillary and 
sublingual salivary glands. The taste fibres run first in the 
lingual and then in the chorda tympani, which conveys them 
to the facial. In the latter they pass to the geniculate ganglion, 






THE FACIAL NERVE 



85 



but their subsequent course to the brain is still doubtful. 
According to Ramsay Hunt, they leave the geniculate ganglion 
in the nervus intermedins, enter the pons and terminate in the 
upper part of the nucleus of the tractus soiitarius (p. 91). 
According to other authorities, they leave the geniculate 




Fig. 45. — Schematic representation of the course of the Taste Fibres. 
Course of taste fibres. Alternative route. 



1. Tongue. 

2. Lingual nerve. 

3. Chorda tympani. 

4. Geniculate ganglion. 

5. Nerve of pterygoid canal (Vidian 

nerve) 



6. Spheno-palatine ganglion. 

7. Maxillary nerve. 

8. Semilunar (Gasserian) ganglion. 

9. Trigeminal nerve. 

10. Facial nerve. 

11. Nucleus of tractus soiitarius. 



12. Glosso-pharyngeal nerve. 

ganglion by the greater superficial petrosal nerve, by which 
they are conveyed to the spheno-palatine ganglion (p. 68) ; 
in this way they reach the maxillary nerve and enter the pons 
in the sensory root of the trigeminal. 

The secretory fibres are stated to arise in the motor nucleus 
of the facial, and they run in the facial nerve until they reach 
the chorda tympani (Fig. 45), by which they are conveyed, 



86 THE NERVOUS SYSTEM 

via the lingual nerve and the submaxillary ganglion, to their 
distribution. 

It is now possible to study the effects of intra-cranial lesions 
of the fibres which constitute the facial nerve. 

Supra-nuclear Lesions may be cortical or subcortical in 
origin. In these cases there is usually some additional par- 
alysis either of the upper limb muscles or of the muscles 
supplied by the hypoglossal (p. 106). Owing to bilateral 
representation in the cerebral cortex, the muscles, though 
much weakened, are not completely paralysed. This applies 
more especially to the muscles of the upper part of the face. 
The orbicularis oculi, to outward appearances, is functioning 
normally, but when the patient endeavours to close the eye 
against resistance, the presence of weakness on the affected 
side is at once determined. 

The mouth is drawn over to the sound side as in the case 
of peripheral lesions, but, in the expression of emotions, the 
two sides of the face become symmetrical, since it is in such 
movements that the muscles around the mouth are most 
commonly associated. 

Since the lesion affects the upper neurones, the electrical 
reactions of the muscles paralysed are unaffected. 

The sensation of taste is not interfered with, and there is no 
disturbance of the salivary or lacrimal secretions. The stapedius, 
being bilaterally represented in the cortex, is not paralysed. 

Nuclear Lesions rarely occur alone and are almost always 
associated with bulbar paralysis (p. 108). An intra-pontine 
haemorrhage may affect either the nucleus or the intra-pontine 
part of the nerve. In this case, the sixth nucleus (or its 
emerging fibres) and the pyramidal tract are also involved 
(Fig. 42). In the resulting paralysis, the sixth and seventh 
nerves are paralysed on the side of the lesion, but the limbs 
are paralysed on the opposite side. This crossed paralysis 
is known as the " Millard-Gubler syndrome " and the position 
of the lesion can be definitely located to the pons. The con- 



i 



THE FACIAL NERVE 87 

dition may be accompanied by some degree of alternate 
hemi-anaesthesia (p. 62). 

Cases of nuclear lesions of the facial have been recorded in 
which the orbicularis oculi and the orbicularis oris have 
escaped paralysis, and they have led to the suggestion that 
these muscles are innervated from the nuclei of the third and 
twelfth nerves respectively. There is, however, no anatomical 
evidence in support of this view, which is founded entirely 
on clinical evidence. 

/;/ lesions of the facial nerve situated betiveen the surface of 
the pons and the geniculate ganglion, the acoustic nerve, which 
is so closely related to the facial in this part of its course, is 
usually involved (Fig. 51). On this account the paralysis of 
the stapedius cannot be determined. According to Ramsay 
Hunt, the sense of taste is lost over the anterior two-thirds of 
the tongue on the affected side, since the lesion is almost 
certain to involve the nervus intermedius. All the facial 
muscles on the affected side are paralysed and, as the lesion 
affects the lower neurone, the electrical reactions become 
altered and the muscles atrophy. 

Lesions affecting the facial tierve between the geniculate gan- 
glion and the origin of the chorda tympani usually result from 
otitis media. The acoustic nerve is not affected and the 
condition of hyperacousis, due to paralysis of the stapedius 
muscle, may sometimes be determined. The sense of taste is 
lost over the anterior two-thirds of the tongue on the affected 
side. The condition of the facial muscles is exactly the same 
as in the lesion described in the preceding paragraph. 

In extra-cranial lesions (p. S2), only muscular paralysis is 
present. The special senses are unaltered. 

The Acoustic or Eighth Cerebral Nerve is made up of 
two parts, termed (a) the Cochlear and (l>) the Vestibular 
nerve. The two meet at the bottom of the internal acoustic 
meatus and run together, within a common sheath, to the 
surface of the pons, where they separate. 



88 THE NERVOUS SYSTEM 

(a) The fibres of the Cochlear Nerve arise in the spiral 




Fig. 46. — Diagram to show the path of the Fibres of the Cochlear Nerve. 



1. Cochlear nerve. 

2. Ventral cochlear nucleus. 

3. Lateral cochlear nucleus. 

4. Striae medullares (acousticae). 

5. Floor of fourth ventricle. 



6. Lateral fillet. 

7. Medial geniculate bod}\ 

8. Inferior corpus quadrigeminuni. 

9. Acoustic radiation. 

10. Cortex of superior temporal gyrus. 



ganglion (of Corti) and they terminate in two nuclei, which 
lie in the lower part of the pons and the upper part of the 



THE ACOUSTIC NERVE 89 

medulla oblongata. A new relay of fibres arises in these 
nuclei and, although some ascend through the same side of 
the brain-stem and do not undergo decussation, the majority 
cross the median plane. Many of the latter lie on the dorsal 
surface of the pons and form transverse ridges, termed the 
strias acousticae, which can be seen in the floor of the fourth 
ventricle (Fig. 32). Having crossed the median plane, the 
acoustic fibres turn upwards and form a tract, known as the 
lateral fillet. This tract ascends through the medulla oblon- 
gata and the pons to terminate in the lower acoustic centres 
— the medial geniculate body (p. 19) and the inferior corpus 
quadrigeminum (p. 18). From these centres new fibres arise 
which at once enter the posterior limb of the internal 
capsule. In this situation they are mingled with ascending 
sensory fibres from the opposite side of the body, but they 
lie in front of the visual fibres and behind the motor fibres 
for the lower limb. After leaving the internal capsule the 
acoustic fibres pass laterally to reach the higher centres, 
which are situated in the cortex of the superior temporal 
gyrus (p. 9). 

Supra-nuclear Lesions of the acoustic tract never cause 
complete deafness unless they are bilateral, on account of the 
connexions of the cochlear nuclei with the cortex of both 
cerebral hemispheres. 

Cortical Lesions may give rise to word-deafness, when they 
occur in the superior temporal gyrus of the left side in right- 
handed individuals. In this condition words can be heard 
as sounds but they cannot be understood. 

Occasionally, in lesions affecting the posterior limb of the 
internal capsule, some degree of unilateral deafness may be 
associated with hemi-ana^sthesia. Cases of hemi-anaesthesia 
accompanied by complete unilateral deafness are always 
hysterical in origin. 

In Infra-nuclear Lesions the cochlear and vestibular nerves 
are often involved together {vide infra, p. 90). In some cases 
the cochlear nerve may be involved alone. It is then necessary 



go THE NERVOUS SYSTEM 

to determine whether the deafness is due to the condition of 
the nerve or to the condition of the conducting apparatus. If 
otoscopic examination is not sufficient, Weber's test may be 
employed. The base of a vibrating tuning-fork is applied to 
the vertex in the median plane. If the unilateral deafness is 
due to an affection of the nervous mechanism, the tuning-fork 
will be heard only, or much more distinctly, on the sound side ; 
on the other hand, if the conducting apparatus is at fault, the 
tuning-fork will be heard better on the affected side. 

(l>) The Vestibular Nerve carries afferent fibres from the 
vestibule and the semicircular ducts (canals). It runs with 
the cochlear nerve from the bottom of the internal acoustic 
meatus to the surface of the brain-stem, where they become 
separated by the restiform body. The fibres of the vestibular 
nerve terminate in several nuclei within the medulla oblongata 
and from these nuclei new fibres arise which connect the 
nerve with the cerebral cortex, the cerebellar cortex and the 
grey matter of the spinal medulla (spinal cord). 

Note. — In the above descriptions of the connexions of the cochlear and 
the vestibular nerves, it has been deemed unnecessary to incorporate any 
more than a rough outline. For a more detailed account the reader must 
consult the standard text-books of Anatomy or Neurology. 

Both the cochlear and the vestibular nerves are affected 
(i) in lesions of the acoustic nerve and (2) in inflammation or 
haemorrhage into the membranous labyrinth (p. 208). 

1. The acoustic nerve may be involved in cerebral tumours 
of the cerebellopontine angle (p. 22), in purulent exudates 
in the cisterna pontis, or in syphilitic meningitis in the 
neighbourhood of the internal acoustic meatus. The symptoms 
directly referable to the acoustic nerve are the same as those 
described in the following paragraph. 

2. Pathological conditions of the labyrinth give rise to a 
train of symptoms, which are grouped together under the name 
of Meniere's disease. The lesion may be of the nature of a 
progressive inflammation or it may take the form of a 
haemorrhage into the labyrinth. The symptoms are naturally 



THE ACOUSTIC NERVE 



9i 



divided into two groups : (a) those referable to the cochlear 
nerve, and (/>) those referable to the vestibular nerve. 

(a) When the disease is slowly progressive in type, tinnitus 
is the symptom which is first noticed. Later, gradually in- 
creasing unilateral deafness becomes more apparent. In the 
case of sudden haemorrhage into the labyrinth, deafness is 
sudden in onset and is, in the first instance, complete. 

(/>) Involvement of the vestibular nerve causes attacks of 
giddiness and vertigo. They may occur in the course of the 




Fig. 47. — Section through Upper Part of Medulla Oblongata. 



1. Pyramidal tract. 

2. Olivary nucleus. 

3. Sensory nucleus of V. 

4. Nucleus of tractus solitnrius. 



5. Nucleus ambiguus. 

6. Nucleus of vagus nerve. 

7. Nucleus of hypoglossal nerve. 

8. Sensory decussation. 



disease without any premonitory symptoms, and the patient 
usually falls to the ground, although he does not necessarily 
lose consciousness. 



The Glosso-pharyngeal or Ninth Cerebral Nerve con- 
tains both motor and sensory fibres. The motor fibres arise 
from the upper extremity of the nucleus ambiguus (p. 94) in the 
upper part of the medulla oblongata. The sensory fibres arise 
in the superior and the petrosal ganglia of the glosso-pharyngeal 
nerve and establish connexions centrally with the tractus 



92 THE NERVOUS SYSTEM 

solitarius, an elongated column of grey matter (Fig. 47) which 
also receives some of the sensory fibres of the vagus. 

The glosso-pharyngeal nerve leaves the medulla oblongata at 
the upper end of the groove between the olive and the restiform 
body (Fig. 8), and passes out of the skull through the jugular 
foramen in company with the vagus and accessory nerves. In 
its extracranial course the nerve is very deeply situated, and 
it inclines downwards and medially in the neck to reach the 
lateral wall of the pharynx. 

Two ganglia, termed the ganglion superius and the gang/ion 
petrosum, are found on the nerve as it lies in the jugular 
foramen. 

The tympanic branch arises from the petrosal ganglion and, 
passing through a minute canal in the petrous temporal, enters 
the middle ear, where it breaks up into a small plexus. A 
branch emerges from this plexus and unites with a small 
branch from the geniculate ganglion of the facial to form the 
lesser superficial petrosal nerve, which ends in the otic ganglion 
(p. 70). In this way the glosso-pharyngeal nerve establishes 
communications with both the mandibular and the facial 
nerves. 

It is said that the secretory fibres for the parotid gland leave 
the glosso-pharyngeal in the tympanic branch and travel in the 
lesser superficial petrosal nerve to the otic ganglion, from 
which they pass directly to the auriculotemporal nerve (p. 74). 

On the lateral wall of the pharynx the glosso-pharyngeal 
nerve breaks up into lingual and pharyngeal branches. The 
lingual branches supply the mucous membrane of the posterior 
third of the tongue with ordinary sensation and with the sense 
of taste, and they extend to the soft palate and the palatine 
tonsil. In nuclear lesions of the tractus solitarius the sense of 
taste is not lost over the posterior part of the tongue. On 
account of the size of the tractus solitarius the results of lesions 
are very variable, but the escape of the taste fibres in such 
lesions has led many authorities to the view that these fibres 
pass to the sensory nucleus of the trigeminal, via the tympanic 






THE GLOSSOPHARYNGEAL NERVE 93 




Fig. 48. — The Lateral Aspects of the Larynx and Pharynx, showing 
their Nerves of Supply. 

Note. — In the upper part of the figure the right ramus of the mandible and the muscles 
(masseter, temporal and pterygoids) attached to it have been removed. 



a. Buccinator. 

/>. Tensor veli palatini. 

c. Levator veli palatini. 

d. Superior constrictor. 

e. Middle constrictor. 
/. Inferior constrictor. 
g. Thyreo-hyoid. 

k. Hyo-gloss 11 i. 



/l. Stylo-hyoid. 

/. Mylo-hyoid. 

;;. Stylo-pharyngeus. 

/. Pharyngeal branch of vagus. 

1. Glosso-pharyngeal nerve. 

■ Superior laryngeal artery. 

3. Superior laryngeal nerve. 

4. External laryngeal nerve. 



5. Recurrent (laryngeal) nerve. 

nerve, the lesser superlieial petrosal nerve, the otic ganglion 
and the mandibular nerve. The pharyngeal branches unite 



94 THE NERVOUS SYSTEM 

with the pharyngeal branch of the vagus to form the pharyngeal 
plexus (p. 96). They supply sensory fibres to the mucous 
membrane of the pharynx and inhibitory fibres to the con- 
strictor muscles. 

The few motor fibres in the glossopharyngeal nerve supply 
the stylo-pharyngeus, which aids in the elevation of the thyreoid 
cartilage during the act of deglutition. It is possible that the 
motor fibres supplied to the tensor veli palatini by the otic 
ganglion (p. 70) are ultimately derived from the glosso- 
pharyngeal through the tympanic plexus [vide supra). 

The glossopharyngeal nerve is never affected alone. The 
motor nucleus is involved in bulbar paralysis (p. 108) and the 
trunk of the nerve may be involved in syphilitic meningitis in 
the posterior cranial fossa, but, in both cases, the tenth and 
the eleventh nerves are also affected, owing to the close rela- 
tionship which exists between the three nerves, as regards both 
their nuclei and their intra-cranial course (Figs. 35 and 47). 

The Vagus or Tenth Cerebral Nerve possesses both motor 
and sensory fibres. The motor fibres arise from the nucleus 
ambiguus, an elongated column of grey matter which extends 
downwards through the medulla oblongata and becomes con- 
tinuous with the anterior column of grey matter in the spinal 
medulla (Fig. 47). 

The sensory fibres end partly in the nucleus of the tractus 
solitarius and partly in the nucleus dorsalis, which lies in the 
dorsal part of the medulla oblongata immediately under the 
lower part of the floor of the fourth ventricle (Fig. 47). 

The emerging fibres of the vagus pass forwards through the 
medulla oblongata and appear in the groove between the olive 
and the restiform body, immediately below the rootlets of the 
glosso-pharyngeal nerve (Fig. 8). 

Together with the latter and the accessory nerve, the vagus 
leaves the skull through the jugular foramen and, in this part 
of its course, it exhibits an enlargement, which is termed the 
jugular ganglion. 




Fig. 49. — The Course, Relations and Branches of the Left Vagus Nerve. 

1. Vagus nerve ; 4. Pharyngeal branch; 5. Internal laryngeal nerve ; 6. External 
laryngeal nerve ; 8. Thyreoid gland ; 9. Cardiac branches; 10. Recurrent (laryngeal) 
nerve; 13. Root of lung; 14, 15, 16. (Esophageal plexus; 17, 18, 19, 20. Gastric 
branches; 21. Hepatic branches ; 24. Glosso-pharyngeal nerve ; 25. Nerve to stylo- 
pharyngeus muscle; 28. Accessory nerve; 31, 32. Sympathetic trunk, a. Left lobe 
of thyreoid gland ; b. Trachea ; c. Left lung ; d. Liver ; c. (Esophagus ; /. Stomach ; 
g. Aortic arch. 



96 THE NERVOUS SYSTEM 

The auricular branch of the vagus (Arnold's nerve) arises 
from the jugular ganglion and, having passed through a small 
canal in the petrous portion of the temporal bone, supplies 
branches to the skin which lines the lateral surface of the 
tympanic membrane and the deep part of the external acoustic 
meatus. This little nerve merits description because the 
stimulation of its terminal fibres may produce symptoms 
which are referred to the areas of distribution of the terminal 
branches of the vagus. Thus, a small piece of wax, impinging 
on the tympanic membrane, may be sufficient to set up gastric 
symptoms, which naturally do not respond to ordinary treat- 
ment. The condition of the ear is often overlooked, as there 
are no local symptoms to direct attention to the cause of the 
disorder (cf. p. 200). 

Immediately below the skull a second peripheral ganglion, 
termed the ganglion nodosum (gang/ion of ike trunk), is placed 
on the vagus. At this point the vagus receives a large branch 
of communication, which represents the whole of that portion 
of the accessory nerve which takes origin in the medulla 
oblongata. The fibres contained in this communicating 
branch are entirely motor and they are destined, principally, 
for ihe supply of the muscles of the larynx and pharynx. 

In addition, the ganglion nodosum establishes communica- 
tions with the hypoglossal nerve, the first cervical nerve and 
the superior cervical ganglion of the sympathetic trunk, but 
the explanation of these connexions is not known. 

The pharyngeal branch of the vagus arises from the ganglion 
nodosum and assists the glosso-pharyngeal nerve in the form- 
ation of the pharyngeal plexus. Through the plexus the vagus 
nerve supplies motor branches, not only to the constrictor 
muscles of the pharynx, but also to the muscles of the soft 
palate, with the possible exception of the tensor veli palatini 
(p. 70). 

In bilateral lesions of the lower neurone {e.g. in post- 
diphtheritic neuritis of the vagus or in bulbar paralysis, p. 108) 
difficulty in swallowing is very pronounced, as the muscular 



THE VAGUS NERVE 97 

walls of the pharynx fail to grip the bolus of food and to help 
it on its way to the oesophagus. In addition, the soft palate- 
is paralysed, and on this account the nasopharynx is not shut 
off from the oral pharynx during deglutition. As a result, the 
food, taking the path of least resistance, regurgitates through 
the nose. A further result of the palatal paralysis is an altera- 
tion in the character of the voice, which acquires a distinctly 
nasal tone. 

The superior laryngeal nerve leaves the vagus at the lower 
end of the ganglion nodosum and passes downwards and 
medially towards the larynx. It breaks up into the internal 
and external laryngeal nerves. 

The internal laryngeal nerve contains sensory fibres only. 
It enters the larynx through the lateral part of the thyro- 
hyoid membrane and supplies the mucous membrane of the 
interior above the level of the vocal folds (true vocal cords). 
A few of its fibres are distributed also to the mucous 
membrane of the recessus piriformis (p. 332). Stimulation 
of the terminal branches of the internal laryngeal nerve sets 
up the cough reflex, and, on this account, the lodgment of a 
particle of food in the recessus piriformis causes a severe 
spasm of coughing, the patient experiencing sensations similar 
to those induced by irritation of the interior of the larynx. 

The external laryngeal nerve is a purely motor nerve, which 
descends in company with the superior thyreoid artery and 
passes under cover of the upper pole of the lateral lobe of the 
thyreoid gland. It gives off one or two small branches to the 
inferior constrictor muscle of the pharynx, but it is mainly 
reserved for the supply of the crico-thyreoid. The contraction 
of this muscle puts the vocal folds (true vocal cords) on the 
stretch, and, when it is paralysed, the pitch of the voice is 
lowered, as the other laryngeal muscles cannot maintain the 
requisite tension (p. 339). 

In the neck the vagus descends vertically in the posterior 
part of the cartoid sheath, in which it lies between the internal 
jugular vein and the common carotid artery. 
7 



9 8 



THE NERVOUS SYSTEM 



Cardiac branches arise from both vagi in the neck and from 
the right vagus and left recurrent (laryngeal) nerves in the 
thorax. These branches constitute the inhibitory nerves of the 
heart, and they are, therefore, antagonistic to the cardiac 




Fig. 50. — Transverse Section through the Neck at the level of the 
First Thoracic Vertebra. 



1. Isthmus of thyreoid gland. 

2. Sterno-hyoid and sterno-thyreoid 

muscles. 

3. Right lobe of thyreoid gland. 

4. Sterno-masto'd muscle. 



5. Right recurrent nerve. 

6. Internal jugular vein. 

7. Common carotid artery. 

8. CEsophagus. 

9. First thoracic vertebra. 



branches from the sympathetic, which act as accelerators of 
the heart-rate. Unilateral Lesions of the vagus cause only 
a transitory disturbance of the heart's action, but Bilateral 
Lesions produce a profound effect. Irritative lesions, such as 
occur in the early stages of post-diphtheritic neuritis, stimulate 



THE VAGUS NERVE 99 

the inhibitory fibres and lead to a slowing of the heart-rate, 
whereas vagal paralysis is followed by definite acceleration of 
the rate, since the sympathetic fibres are no longer opposed. 

The recurrent (laryngeal) nerves arise at different levels on 
the two sides of the body. The right recurrent nerve leaves 
the vagus as it crosses the subclavian artery at the root of the 
neck. It hooks round behind the termination of the innomin- 
ate artery and then ascends in the groove between the oeso- 
phagus and the trachea (Fig. 50), where it comes into close 
contact with the lateral lobe of the thyreoid gland. 

The left recurrent nerve arises from the vagus as it crosses 
the arch of the aorta in the thorax. It passes backwards 
below the aortic arch and then upwards behind it. In the 
first part of its course the left recurrent nerve lies a little 
above the left bronchus and it may be compressed against 
the aortic arch, when the bronchus is displaced upwards by 
enlargement of the left atrium (auricle) of the heart in mitral 
stenosis. It then ascends through the thorax in the groove 
on the left side of the trachea (p. 339) and enters the neck, 
where its relations are similar to those already described for 
the recurrent nerve of the right side. 

The recurrent nerve supplies most of the intrinsic muscles 
of the larynx, and its sensory fibres are distributed to the 
laryngeal mucous membrane below the level of the vocal 
folds (true vocil cords). 

Owing to its longer course, the left recurrent nerve is 
subjected to pressure more often than the right. It may be 
compressed — (1) By aneurisms of the aortic arch (p. 319); 
(2) by mediastinal tumours or enlarged mediastinal lymph 
glands ; (3) by the left bronchus (vide supra). The right 
recurrent may be compressed near its origin by aneurism of 
the terminal part of the innominate artery. Lastly, either or 
both nerves may be affected in enlargements of the thyreoid 
gland. 

The various results of paralysis of the recurrent nerves 
are described on page 338. 



ioo THE NERVOUS SYSTEM 

Within the thorax, the right vagus descends on the right 
side of the trachea and then passes behind the root of the 
right lung. In this part of its course, it is exposed to 
pressure from mediastinal tumours or enlarged mediastinal 
lymph glands. The left vagus crosses the left or anterior 
aspect of the arch of the aorta and then passes behind the 
root of the left lung. Both vagi assist in the formation of 
the pulmonary plexuses, in which they unite with branches 
from the sympathetic. The pulmonary branches of the vagi 
are said to supply the circular muscular coats of the bronchi, 
and they are believed by some authorities to be at fault in 
the condition of spasmodic asthma. 

On leaving the roots of the lungs, the two vagi pass 
downwards on the oesophagus and form the oesophageal 
plexus. They leave the thorax in company with the oeso- 
phagus and enter the abdomen, where their terminal branches 
are distributed to the stomach and, probably, also to the 
liver and the small intestine. 

Summary. — The vagus nerve, therefore, is responsible for 
the motor supply of — (i) The soft palate; (2) the pharyngeal 
muscles ; (3) the laryngeal muscles ; (4) the heart — inhibitory : 
(5) the oesophagus, stomach, etc. ; and (6) the bronchial 
muscles (?). It conveys afferent impulses from — (1) The 
stomach and oesophagus; (2) the heart; (3) the larynx, 
bronchi and lungs ; and (4) the external acoustic meatus 
(p. 199). 

All these structures may be affected in lesions of the nerve 
or its nuclei (p. 94) ; and any one of them may be affected 
reflexly in pathological conditions of one of the others 
(cf. pp. 190 and 195). 

Supra-nuclear Lesions produce no noticeable effects, 
unless they are bilateral. Any paresis that may exist is 
completely masked, owing to bilateral representation of the 
muscles in the cerebral cortex (p. 34). 

Nuclear Lesions are of fairly common occurrence. They 
are usually bilateral and constitute a part of a slowly progressive 



THE VAGUS NERVE 101 

condition, which is termed bulbar paralysis. Reference is 
made to this condition on page 108. 

Infra-nuclear Lesions, when bilateral as in post- 
diphtheritic neuritis, result in complete paralysis of the 
muscles supplied by the vagi. The constrictors of the 
pharynx and the muscles of the soft palate are affected, 
causing difficulty in swallowing and in pronunciation (p. 108). 
The ary-epiglottic muscles (p. 332) may be involved, and, 
if so, there is grave danger of inspiration pneumonia. 
Owing to paralysis of the cardiac inhibitory nerves, the rate 
of the heart's action becomes greatly accelerated. The effects 
on the lungs, oesophagus and stomach are not easily determin- 
able, but they would appear to be relatively of little importance. 

Unilateral Lesions may affect the vagus in its course 
from the medulla oblongata to the jugular foramen, and they 
are usually caused by inflammatory conditions of the dura 
mater. The glossopharyngeal, the accessory and, probably, 
the hypoglossal nerves will be affected at the same time (Fig. 
51), but the direct results of this extensive paralysis are not 
so serious as might be expected, because a good degree of 
compensation is obtained, owing to overaction of the lingual, 
palatal, pharyngeal and laryngeal muscles of the sound side. 

The vagus nerve may be affected alone below the level 
of the greater cornu of the hyoid bone. If the lesion occurs 
above the point of origin of the recurrent (laryngeal) nerve, 
the symptoms are precisely the same as are found in lesions 
of that nerve (p. 338). When the vagus is involved below the 
origin of the recurrent nerve, no characteristic symptoms are 
produced. 

The Accessory or Eleventh Cerebral Nerve is purely 
motor in function. It consists of a cerebral and a spinal 
portion, but the two are only related intimately as they pass 
through the jugular foramen. 

The cerebral portion arises from the lower part of the nucleus 
ambiguus (p. 94), and its fibres emerge from the medulla 



I02 



THE NERVOUS SYSTEM 



oblongata in the lower part of the groove between the olive 
and the res ti form body. After leaving the skull, it joins the 




Fig. 51. — Interior of the Skull after the removal of the Brain, showing the 
poinls of exit of the twelve cerebral nerves. 

ganglion nodosum of the vagus, and it should really be con- 
sidered as a part of the vagus nerve (p. 96). 

The spinal portion arises from the anterior column of grey 
matter in the spinal medulla, and its rootlets emerge on the 



THE ACCESSORY NERVE 103 

lateral aspect of the spinal medulla, midway between the 
anterior and posterior roots of the upper five cervical nerves. 
They ascend in the vertebral canal, forming a common trunk, 
which enters the cranium through the foramen magnum and 
passes to the jugular foramen. Outside the skull the spinal 
portion of the accessory runs downwards, backwards and 
laterally through the neck (Fig. 49), and it is entirely distributed 
to the sterno mastoid and the upper part of the trapezius. 

The sterno- mastoid arises from the manubrium sterni and 
the medial third of the clavicle and passes upwards, backwards 
and laterally to be inserted into the mastoid process and the 
occipital bone. Contraction of the muscle approximates its 
insertion to its origin, and therefore the mastoid process is 
approximated to the manubrium, i.e. the head is rotated 
towards the opposite side and, at the same time, the chin is 
tilted upwards. 

The upper part of the trapezius arises from the external 
occipital protuberance and the ligamentum nuchas, and its 
fibres pass downwards and laterally to be inserted into the 
lateral third of the clavicle. When the muscle contracts, it 
elevates the point of the shoulder and, in association with 
the serratus anterior (s. magnus), rotates the scapula clock- 
wise (as viewed from in front), enabling the arm to be flexed 
and abducted beyond a right angle (p. 132). Further, when 
the body is in the erect or sitting posture with the arms 
unsupported, the weight of the upper limb is partially borne 
by the upper portion of the trapezius. 

Supra-nuclear Lesions of the fibres of the spinal portion 
of the accessory nerve are never isolated, and occur most 
commonly in cerebral hemiplegia in company with extensive 
paralysis of the limb muscles. The skrno-mastoid, though 
weakened, is not paralysed, since it is innervated from the 
cortex of both cerebral hemispheres. The upper part of the 
trapezius is not completely paralysed, but the point of the 
shoulder, being depressed by the weight of the limb, occupies 
a lower level than the point of the sound shoulder. 



104 THE NERVOUS SYSTEM 

Nuclear Lesions occur in the late stages of progressive 
muscular atrophy or as the result of a downward spread in 
bulbar paralysis (p. 108). Since the lesion is bilateral, both the 
sterno-mastoids and both the trapezius muscles are paralysed. 
The head therefore falls forward and cannot be extended on 
the trunk. This condition, however, is not wholly referable 
to the trapezius, as the deeper muscles at the back of the 
neck are also involved. 

Infra-nuclear Lesions of the accessory nerve may occur 
(a) in the anterior triangle of the neck, and (l>) in the posterior 
triangle. 

(a) Neuritis of the accessory gives rise to the condition of 
spasmodic torticollis, which is due to spasmodic contraction 
of the sterno-mastoid, on the side of the lesion. This 
condition may be accompanied by spasm of the upper fibres 
of the trapezius, resulting in spasmodic elevations of the point 
of the shoulder, which synchronise with the torticollis. 

Paralysis of the sterno-mastoid is marked by tonic torti- 
collis, which is not always pronounced, but in this case the 
condition is due to the tonus of the unopposed muscle of 
the sound side. 

When the trapezius is paralysed, the point of the shoulder on 
the affected side drops to a lower level, because, under normal 
conditions, the upper part of the muscle helps to support the 
weight of the upper limb. In addition, since the lower neurone 
is affected, the muscles atrophy and exhibit alterations in their 
electrical excitability. Owing to atrophy of the trapezius, the 
normal rounded contour of the side of the neck is lost and 
the resulting "square" appearance is quite characteristic. 

(b) When the accessory nerve is injured in its course across 
the posterior triangle, only the trapezius is affected. As the 
injury is commonly caused by heavy weights, carried on the 
shoulder, the long thoracic nerve (of Belt) may also be involved 
and the deformity is more complicated (p. 133). 

The Hypoglossal or Twelfth Cerebral Nerve is purely 



THE HYPOGLOSSAL NERVE 



io: 



motor in function. It arises from a nucleus which is situated 
in the dorsal part of the medulla oblongata (Fig. 52) and which 
is continuous below with the anterior column of grey matter 
in the spinal medulla. The fibres pass forwards through the 
substance of the medulla oblongata and come into close 
relationship with the pyramidal tract, before they emerge 
from the groove between the pyramid and the olive (Fig. 8). 
As it runs laterally from the medulla oblongata, the hypo- 
glossal nerve lies below the ninth, tenth and eleventh nerves 
in the posterior cranial fossa. It passes through the hypo- 




FlG. 52. — Section through Upper Part of Medulla Oblongata. 
1. Pyramidal tract. 2. Olivary nucleus. 7. Nucleus of hypoglossal nerve. 

glossal canal (anterior condyloid foramen), which pierces the 
occipital bone just above the condyle. Consequently, after 
leaving the skull, the nerve descends close to the lateral 
aspect of the atlanto-occipital joint. On this account, it may 
be involved in tuberculous disease of the articulation, and 
paralysis and atrophy of one half of the tongue is a valuable 
localising symptom in cervical caries. 

In its extra-cranial course, the hypoglossal nerve is at first 
related to the ninth, tenth and eleventh nerves, but it passes 
forwards on a level with the greater cornu of the hyoid bone 
to reach the tongue. 



io6 THE NERVOUS SYSTEM 

In the upper part of the neck, the hypoglossal nerve receives 
a branch of communication from the anterior ramus (primary 
division) of the first cervical nerve. This communication 
leaves the nerve in three parts, which are all distributed to 
muscles acting on the hyoid bone. The first part constitutes 
the ramus descendens hypoglossi, which unites with the ramus 
descendens cervicalis(C. 2 and 3) to form the ansa hypoglossi. 
From the loop thus formed the sternohyoid, the sterno- 
thyreoid and the omohyoid muscles receive their nerve 
supply. The second part supplies the thyreo-hyoid ; the third 
part is distributed to the genio-hyoid. 

The sterno-thyreoid passes upwards from the posterior aspect of the 
manubrium sterni to the lateral aspect of the thyreoid cartilage and, as it 
ascends, it covers the lateral lobe of the thyreoid gland. 

The stemo-hyoid covers the medial pirt of the sterno-thyreoid and extends 
upwards to the hyoid bone. 

The omo-hyoid is a digastric muscle. Its posterior belly runs medially 
from the upper border of the scapula and, under cover of the sterno- 
mastoid, ends in the common tendon, which is held down to the medial 
end of the clavicle by a slip of the deep cervical fascia. Its anterior belly 
runs upwards, superficial to the sterno-thyreoid and along the lateral 
border of the sterno-hyoid, to reach the hyoid bone. 

The thyreo-hyoid may be regarded as the upward continuation of the 
sterno-thyreoid to the hyoid bone. 

These four muscles depress the hyoid bone and larynx in the last stage 
of the act of deglutition, and they have a steadying action when these 
structures are being elevated. 

Paralysis of this group, combined with paralysis of the 
tongue on the same side, is symptomatic of a lesion of the 
hypoglossal nerve in the first part of its extra-cranial course. 
Owing to paralysis of the depressors, the tonus of the un- 
opposed elevators (mylo-hyoid and digastric) causes the greater 
cornu of the hyoid bone to lie at a higher level on the side of 
the lesion. When the muscles become atrophied, the condition 
is readily recognised on palpation of the thyreoid cartilage. 

The genio-hyoids are two short muscles which extend from the deep 
surface of the mandible at the symphysis to the hyoid bone. They lie deep 
to the mylo-hyoids and aid them in elevating the hyoid bone and larynx. 



THE HYPOGLOSSAL NERVE 107 

The terminal branches of the hypoglossal nerve are dis- 
tributed to the muscles of the tongue. This group includes 
the styloglossus, the hyo-glossus, the genio-glossus and the 
intrinsic muscles. 

The fibres which are distributed by the facial nerve to the 
orbicularis oris muscle are said to arise in the hypoglossal 
nucleus. They then ascend to join the facial nerve of the 
same side (p. 87). 

Supra-nuclear Lesions produce little effect on the tongue 
muscles, owing to their bilateral representation in the cerebral 
cortex. If they occur in the internal capsule, a true deviation 
of the protruded tongue may be present, owing to weakening 
of the genio-glossus {vide infra). 

Nuclear Lesions are usually bilateral (bulbar paralysis, 
p. 108). The tongue lies motionless in the floor of the mouth 
and deglutition is, therefore, practically impossible. The 
orbicularis oris is also affected, and the combined paralysis 
of tongue and lips has a serious effect on the speech. 

Infra-nuclear Lesions. — In rare cases, the fibres of the 
hypoglossal may be interfered with as they traverse the 
medulla oblongata. The site of the lesion is usually indicated 
by a crossed paralysis, the limbs being affected on the opposite 
side of the body, owing to injury of the pyramidal tract above 
the decussation (Fig. 52). 

In unilateral hypoglossal paralysis, the characteristic sign 
is deviation of the protruded tongue to the paralysed side. 
This is principally due to the action of the unopposed genio- 
glossus of the sound side, which arises from the posterior 
aspect of the symphysis menti and spreads backwards and 
laterally into the tongue. Owing to the lateral inclination 
of some of its fibres, the unopposed genio-glossus drags the 
lateral border of the dorsum of the tongue towards the median 
plane and thus the tongue, as a whole, is pulled over to the 
side of the lesion. Difficulty in the pronunciation of the 
lingual consonants also accompanies unilateral paral>sis of 
the tongue muscles, and speech is therefore rendered indistinct. 



10S THE NERVOUS SYSTEM 

Bulbar Paralysis. — As the motor nuclei of the ninth, 
tenth, twelfth and the cerebral portion of the eleventh are 
intimately related to one another in the medulla oblongata (Fig. 
52), it is not surprising to find that they may all be involved in 
certain, slowly progressive, degenerative processes. Further, 
as the nucleus ambiguus (p. 94) and the hypoglossal nucleus 
represent the upward continuation of the anterior column of 
the grey matter of the spinal medulla, the spread of the pro- 
cess from the one to the other is of common occurrence. 

The term bulbar paralysis is applied to lesions affecting the 
motor nuclei of the medulla oblongata, whether they occur 
as the starting-point of a downward spreading process or in 
the later stages of an upward spreading process, e.g. pro- 
gressive muscular atrophy (p. 46). The symptoms vary in 
different cases, as the disease does not attack the groups of 
cells within the nuclei in any fixed order. 

As a rule, the hypoglossal nuclei are first involved, and 
weakness of the tongue muscles and the orbicularis oris 
(p. 107), causing difficulties in speech and deglutition, are 
often the first signs that a case of progressive muscular 
atrophy has entered on its last stage. Later, the muscles of 
the pharynx and soft palate are involved and the patient 
becomes unable to swallow. Paralysis of the laryngeal 
muscles is not usually very noticeable, but, when the ary- 
epiglottici (p. 332) are affected early there is grave danger of 
aspiration pneumonia. 

The same symptoms may arise suddenly, owing to small 
haemorrhages or areas of embolic softening in the medulla 
oblongata. The distinctive term "acute bulbar paralysis" has 
been given to this condition. 

THE MEMBRANES OF THE BRAIN 

The brain is surrounded by three membranous layers, 
termed the dura mater, the arachnoid and the pia mater. 
The spaces separating these membranes from one another 



THE DURA MATER 109 

contain a clear serous fluid (p. 23), which serves to protect 
the brain from laceration and contusion. 

The Dura Mater constitutes the outermost covering and is 
the strongest of the three membranes which invest the brain. 
It is usually described as consisting of an inner, serous and 
an outer, fibrous layer, but the latter is really the endo- 
periosteum, which lines the cranial cavity and is everywhere 
closely applied to the bone, being specially adherent to the 
floor of the skull. 

The serous layer of the dura mater lines the cavity in which 
the brain lies, and it is separated from the arachnoid by the 
subdural space, which contains the clear, subdural fluid. 
No communications exist between the subdural and the sub- 
arachnoid spaces, and the passage of fluid from one space 
to the other occurs by a process of osmosis through the 
arachnoid. There is no marked difference between the sub- 
dural fluid and the cerebro-spinal fluid, which is found in the 
subarachnoid space, and it is therefore immaterial which of 
the two is drawn off for examination in a lumbar puncture 
(p. 41). In fractures of the skull, the discharge of serous 
fluid from the nose or acoustic meatus indicates that the serous 
layer of the dura mater has been injured. 

The falx cerebri is a longitudinal crescentic fold of the 
serous layer. It dips into the longitudinal fissure and par- 
tially separates the two cerebral hemispheres from one another. 
Its anterior extremity is attached to the ethmoid bone, but its 
intermediate portion has a free lower margin, which overhangs 
the corpus callosum. Posteriorly, the two layers of the falx 
cerebri are continuous, on each side, with the upper layer of 
the tentorium cerebelli (Fig. 53). 

The tentorium cerebelli is a transverse fold of the serous 
layer, which projects into the posterior part of the cranial 
cavity from behind and from the sides. It forms a partition 
which separates the cerebellum below from the cerebral hemi- 
spheres above. Its peripheral border is attached to the 
upper margin of the posterior cranial fossa, but its anterior 



I IO 



THE NERVOUS SYSTEM 



border is free, and, together with the dorsum sells of the 
sphenoid bone, bounds an aperture through which the mid- 
brain passes to reach the cerebrum (Fig. 53). 

The Arachnoid is a much more delicate membrane than 
the dura mater, and it differs still further from the latter in 
being more intimately related to the brain. 

The Pia Mater, which lies subjacent to the arachnoid, dips 




Fig. 53. — The Cranial Blood Sinuses. The left half of the skull and 
the left cerebral hemisphere have been removed. 



1. Falx cerebri. 



2. Tentorium cerebelli. 



into all the sulci on the surface of the brain, but the arachnoid 
merely bridges over their margins. Over the various con- 
volutions the two membranes are closely applied to one 
another, and in these areas the subarachnoid space is prac- 
tically obliterated. In certain areas, however, definite 
intervals exist between the arachnoid and the pia mater. 
These parts of the subarachnoid space are termed cisternce, and 
the more important of them are situated on the basal surface 
of the brain. 



THE CISTERNS in 

The cisterna interpeduncularh {basalts) lies over the inter- 
peduncular fossa and it contains the third, fourth and sixth 
cerebral nerves, and the optic tracts in a part of their course. 
In basal meningitis, purulent exudates are found in the 
cisternal and, when the cisterna interpeduncular is im- 
plicated, ocular paralysis or visual disturbances are of common 
occurrence. 

1 he cisterna fossa lateralis cerebri lies in relation to the 
anterior perforated substance (p. 16) and contains the middle 
cerebral artery. It is through, this cisterna that the purulent 
exudate spreads to the lateral surface of the brain in tuber- 
culous bjsal meningitis. 

The cistern i cerebello-medullaris {c. magna) lies between 
the cerebellum and the lower part of the roof of the fourth 
ventricle. In this region the roof is extremely thin and con- 
sists of ependyma and the covering pia mater. The cisterna 
cerebello-medullaris communicates with the interior of the 
ventricular system through three small foramina, which 
pierce the thin roof and, as a result of these communi- 
cations, the cerebro-spinal fluid (p. 23) is able to drain away 
into the subarachnoid space. When the foramina are closed 
by adhesions, as may happen following meningitis, this outlet 
is shut off and the fluid accumulates within the ventricles, 
giving rise to acquired hydrocephalus. It is also owing to 
these communications that turbulent fluid is frequently found 
inside the ventricles in association with the presence of puru- 
lent exudates in the subarachnoid space. 

A small, unnamed cisterna lies over the " cerebello pontine 
angle" (p. 22) and it is traversed by the fifth, seventh and 
eighth cerebral nerves. This cisterna is a favourite site for 
purulent exudations in cerebro-spinal meningitis, and, there- 
fore, paralysis of the nerves mentioned is a not uncommon 
sequela of the disease. 

The Cranial Blood Sinuses are placed between the serous 
layer of the dura mater and the endo-periosteum of the skull. 



I 12 



THE NERVOUS SYSTEM 



The additional support which they gain in this way is 
required, for their walls are extremely thin and consist of 
little more than a lining of endothelium. On this account 
severe haemorrhage occurs when a sinus is wounded, as its 
walls do not collapse like those of other veins. The cranial 



Corpus callosum 



Septum pellucidum 



Interventricular foramei — 

Lamina terminalis 



Ojulo-motor nerve 



_ _- Middle commissure 



Pineal body 
Corpora quadrigemina 
„ Cerebral aqueduct 
(of Sylvius). 

_, Fourth 
ventricle 




Central canal of 

~ spinal medulla 



Fig. 54. — Median Sagittal Section through the Brain-Stem, showing the 
third and fourth ventricles and their connexions. 



sinuses establish numerous connexions with the veins outside 
the skull, and these communications are of great practical 
importance, because, as they possess no valves, they afford 
channels for the spread of septic thrombi. 

The Superior Sagittal (Longitudinal) Sinus lies in the 
upper border of the falx cerebri. It begins anteriorly at the 



THE CRANIAL SINUSES 



"3 



foramen crecum of the ethmoid, through which it may 
communicate with the veins of the nasal mucous membrane. 
Owing to this communication, epistaxis may occur in children, 




Fig. 55.— The Cranial Blood Sinuses. The left half of the skull and 
the left cerebral hemisphere have been removed. 



A. 


Anterior cerebral artery. 






Frontal air sinus. 


B. 


Great cerebral vein (of Galen). 




h. 


Lateral pterygoid lamina. 


C. 


Superior sagittal sinus. 




J- 


Mandibular (glenoid) fossa 


D. 


Inferior sagittal sinus. 




I. 


Maxilla. 


E. 


Straight sinus. 




1. 


Falx cerebri. 


F. 


Superior petrosal sinus. 




2. 


Tentorium cerebelli. 


G. 


Transverse (lateral) sinus. 




3- 


Optic nerve. 


a. 


Scalp. 




4- 


Cut edge of dura mater. 


i. 


Cut edge of skull. 




5- 


Mandibular nerve. 


c. 


Mastoid process. 




6. 


Tuberosity of maxilla. 


d. 


Styloid process. 




7- 


Ophthalmic nerve. 


e. 


Foramen ovale. 




8. 


Corpus callosum. 


/■ 


Maxillary nerve. 

10. 


Mi 


9- 
J- brain. 


Pineal body. 



following an increase of intra-cranial tension such as ac- 
companies a fit of temper. The foramen caecum is usually 
patent in young children, but it may become closed at a 



later stage. 



1 1 4 THE NERVOUS SYSTEM 

The superior sagittal sinus passes backwards and, at the 
posterior end of the falx cerebri, it reaches the internal occipital 
protuberance, where it bends sharply, usually to the right, to 
form the transverse (lateral) sinus. In its course, the superior 
sagittal sinus receives numerous tributaries from the surface of 
the brain and, through a foramen in each parietal bone, it 
communicates with the veins of the scalp. Through this 
connexion septic infections of the scalp may give rise to 
thrombosis of the sinus. 

The Inferior Sagittal (Longitudinal) Sinus lies in the free, 
lower border of the falx cerebri and, at its posterior end, 
unites with the great cerebral vein (of Galen, p. 27) to 
form the straight sinus. It receives tributaries from the 
medial surfaces of the cerebral hemispheres. 

The Straight Sinus runs backwards over the upper surface 
of the tentorium cerebelli in the lower border of the falx 
cerebri, until it reaches the internal occipital protuberance, 
where it bends sharply, usually to the left, to form the 
transverse (lateral) sinus. It receives tributaries from the 
occipital lobes and from the cerebellum. 

The Transverse (Lateral) Sinus of the right side is con- 
tinuous with the superior sagittal sinus, while that of the left 
side is continuous with the straight sinus. It begins at the in- 
ternal occipital protuberance and runs laterally in the attached, 
peripheral border of the tentorium cerebelli. When it reaches 
the mastoid part of the temporal bone, it passes downwards, 
forming a deep groove in the side wall of the posterior 
cranial fossa. In this part of its course, the transverse sinus 
lies behind the tympanic {mastoid) antrum, which is contained 
within the posterior part of the petrous temporal, and it 
communicates with the posterior auricular vein of the scalp 
through the mastoid foramen. Finally, it passes through the 
jugular foramen and becomes continuous with the internal 
jugular vein. 

The transverse sinus is joined by the superior petrosal 
sinus, which connects it to the cavernous sinus, and by 



THE CRANIAL SINUSES 



"5 



numerous cerebral and cerebellar veins. On account of its 
proximity to the tympanic (mastoid) antrum, the sinus may 
become the site of a septic thrombus in inflammatory condi- 
tions of the antrum, and the infection may spread backwards 
along the cerebellar veins, ultimately giving rise to a cerebellar 
abscess. 

The Cavernous Sinuses lie one on each side of the body of 
the sphenoid in the middle cranial fossa. At its anterior end, 




FlG. 56. — Transverse Section through the Cavernous Sinus. 

7 



1. Hypophysis. 

2. Endothelial wall of sinus 

3. Cavernous sinus. 

4. Internal carotid artery. 

5. Oculo-motor nerve. 

6. Abducent nerve. 



Trochlear nerve. 

8. Serous layer of dura mater. 

9. Ophthalmic nerve. 
10. Sphenoidal air-sinus. 

n. Endo-periosteum of skull. 
12. Maxillary nerve. 



each sinus receives the ophthalmic veins, which bring it into 
communication, indirectly, with the veins of the face. From 
its posterior end, the superior and inferior petrosal sinuses 
pass backwards to join, respectively, the transverse sinus and 
the internal jugular vein. In addition, each cavernous sinus 
communicates with the veins of the pterygoid plexus through 
the foramen ovale and through the foramen of Vesalius, when 
the latter is present. The pterygoid veins are tributaries of 
the internal maxillary vein, which receives all the alveolar 
(dental) and a few pharyngeal veins. In this way the latter 



n6 THE NERVOUS SYSTEM 

groups are brought into communication with the cavernous 
sinus. 

Owing to its numerous communications, the cavernous 
sinus may become the site of a septic thrombosis following 
infective processes of the face, orbit, teeth or naso-pharynx. 
The condition is usually accompanied by paralyses of the ocular 
muscles and there may be sensory disturbances over the area 
supplied by the ophthalmic nerve (Fig. 41). These com- 
plications are due to the intimate relation which the third, 
fourth, sixth and ophthalmic nerves bear to the cavernous 
sinus, for, after they pierce the serous layer of the dura mater 
and before they enter the orbit, they lie in the lateral wall of 
the sinus, between the supporting dura mater and the lining 
endothelium (Fig. 56). 

The Blood-supply of the Brain and its Membranes. 
— The dura mater receives its blood-supply from the meningeal 
arteries, which are placed between the endo-periosteum and 
the serous layer. Of these the most important is the middle 
meningeal artery. It arises from the internal maxillary artery, 
which is one of the terminal branches of the external carotid, 
and, entering the skull through the foramen spinosum, runs 
forwards and laterally over the floor of the middle cranial fossa. 
Its anterior branch runs upwards towards the vertex along 
a line which may be said to correspond to the pre-central 
sulcus (Fig. 3), and, when it is torn, the resulting blood- 
clot exercises pressure on the neighbouring anterior central 
gyrus (p. 5). The area involved and, consequently, the 
symptoms will depend on the site of the clot, but, owing 
to their position, the motor centres for the lower limb 
(p. 5) are never affected in the first instance. Unless 
the dura mater is ruptured, the haemorrhage is extra-dural in 
position. 

The posterior branch of the middle meningeal artery runs 
backwards along a line which lies a little above the level of 
the middle temporal sulcus. Rupture of this division will not, 



THE MENINGEAL VESSELS 



117 



in the first instance, produce any motor paralysis, but it will 
lead to pressure on the higher auditory centres. These 
effects, however, cannot be recognised owing to the accom- 
panying loss of consciousness. 




Fig. 57. — Lateral Aspect of Skull, showing the relations of important 
structures to the surface. 



1. Zygomatic arch. 

2. Middle meningeal artery. 

3. Greater wing of sphenoid. 

4. Glabella. 

5. Temporal line. 

6. Anterior branch of middle meningeal 

aitery. 

7. Central sulcus (of Rolando). 

8 Coronal suture. 

9 Lateral fissure, posterior ramus. 



10. Superior temporal sulcus. 

11. Posterior branch of middle meningeal 

artery. 

12. Line drawn from floor of orbit 

through centre of external acous- 
tic meatus. 

13. External occipital protuberance. 

o 1 . Site for puncture of lateral ventricle. 
o-. Site for puncture of inferior horn of 
lateral ventricle.] 



The walls of the meningeal veins are very similar in 
structure to the walls of the cranial blood sinuses, and they 
consist of an endothelial layer and a slight amount of 
supporting fibrous tissue. On this account they are easily 
torn, and in most cases meningeal hremorrhage has its source in 
the veins and not in the arteries. 



n8 



THE NERVOUS SYSTEM 



The Cerebral Arteries. — Four large arteries enter the 
cranial cavity to supply the brain, and in the neighbourhood 




Fig. 5S. — Interior of the Skull after the removal of the Brain, showing the 
points of exit of the twelve cerebral nerves. 



of the interpeduncular fossa they become interconnected so as 
to form the arterial circle (of Willis). 

The Internal Carotid Artery enters the skull through a 
special canal in the petrous temporal and passes forwards in 



THE CEREBRAL ARTERIES 119 

the lateral wall of the cavernous sinus, lying between the 
endoperiosteum and the endothelial lining. At the anterior 
clinoid process (Fig. 58) it pierces the dura mater and, 
opposite the anterior perforated substance (spot), it ends by 
dividing into the anterior and middle cerebral arteries. 

The Middle Cerebral Artery inclines laterally across the 
anterior perforated substance and enters the lateral fissure (of 
Sylvius). It then courses over the surface of the island (of 
Reil) and extends backwards in the posterior ramus of the 
lateral fissure. It gives off a number of cortical branches, 
which emerge from the fissure and supply the whole of the 
lateral surface of the hemisphere, with the exception of a strip 
along its superior and inferior margins. Further, they do not 
supply the occipital lobe. The middle cerebral artery, there- 
fore, supplies — (1) The whole of the motor area, except the lower 
limb centres; (2) the motor speech centre; (3) the centre for 
written speech; (4) the word-hearing centre; and (5) the 
word-seeing centre (Fig. 3). 

As it crosses the anterior perforated substance, the middle 
cerebral artery gives off several central branches, which at once 
pass upwards and enter the brain. They thus come into 
relationship with the lentiform nucleus (p. t,t,) and they 
ascend across its lateral surface for a short distance before 
they pass medially into its substance. The lenticulo striate 
arteries traverse the anterior part of the lentiform nucleus and 
the anterior limb of the internal capsule and terminate in the 
head of the caudate nucleus. The lenticulo-optic arteries are 
placed more posteriorly, and consequently pass through the 
posterior limb of the internal capsule before they reach the 
thalamus. The artery of cerebral haemorrhage belongs to 
the former group. 

The central arteries, as they lie in the brain substance, are 
poorly supported and they are, in consequence, frequently 
the site of small aneurismal dilatations. When small emboli 
are carried into the middle cerebral artery, they are usually 
arrested in the cortical branches and only rarely enter the 



!2o THE NERVOUS SYSTEM 

central branches, owing to the upward course which these 
arteries take. 

The Anterior Cerebral A?-tery, at its origin from the internal 
carotid, at once bends abruptly in a medial direction to gain 
the posterior extremity of the longitudinal fissure. It then 
bends sharply forwards and is continued round the genu of 
the corpus callosum in company with the artery of the oppo- 
site side. Together they extend backwards at the bottom of 
the longitudinal fissure until they reach the parietal lobes. 

The anterior cerebral artery is responsible for the supply 
of the whole of the medial aspect of the hemisphere as 
far back as the precuneus, and, in addition, its cortical 
branches emerge from the longitudinal fissure to supply the 
cortex of the lateral and orbital aspects near their margins. 
The anterior cerebral artery, therefore, supplies the upper 
extremity of the precentral gyrus, which contains the motor 
centres for the lower limb. 

The Vertebral Artery, which arises from the first part of 
the subclavian in the root of the neck, passes upwards, 
traversing the foramina in the transverse processes of the 
cervical vertebrae, and enters the skull through the foramen 
magnum. Within the skull, it ascends on the lateral aspect 
of the medulla oblongata and inclines medially to meet its 
fellow of the opposite side in the median plane at the lower 
border of the pons. At this point the two vertebral arteries 
unite to form the Basilar Artery, which passes upwards in 
the median plane to the upper border of the pons, where it 
divides into the two posterior cerebral arteries. 

The Posterior Cerebral Artery rans laterally and backwards 
round the mid-brain, to which it supplies central branches. 
Its cortical branches are distributed to the posterior two- 
thirds of the inferior surface of the cerebral hemisphere, 
and, in addition, they supply the cortex of the whole of the 
occipital lobe. The posterior cerebral artery is, therefore, 
responsible for the blood-supply of the higher visual centres, 
and, on this account, an embolus which finds its way into 



THE CEREBRAL ARTERIES 121 

this artery gives rise to the condition of homonymous 
hemianopia (p. 52). 

The Arterial Circle (of Willis) brings the six cerebral 
arteries into communication with one another. As the two 
anterior cerebrals lie side by side in the longitudinal fissure, 
they are connected to one another by the anterior communi- 
cating artery, which thus links up the two carotid systems. 
Each internal carotid artery is connected to the posterior 
cerebral of its own side by the posterior communicating artery, 
and thus the two carotid systems are linked up with the 
basilar system. This arterial anastomosis provides a means 
for the re-establishment of the circulation when any of the 
great cerebral blood-vessels is obstructed outside the skull. 

When emboli are carried along the internal carotid artery 
into the skull, they usually pass into the middle cerebral 
artery, owing to the abrupt bend which the anterior cerebral 
makes at its origin. In cortical lesions due to this cause, 
the prognosis is good and almost complete recovery may be 
expected, because the cortical branches of the cerebral arteries 
anastomose with one another, although not with any degree 
of freedom On the other hand, the central branches are all 
end-arteries, i.e. they do not establish any anastomoses with 
one another, and, on this account, obstruction to the blood- 
supply of any central area will, unless very transient, always 
be followed by necrosis of practically the whole of that area. 

The Veins of the Brain are divided into a superficial and 
a deep group. The superficial veins lie in the subarachnoid 
space and terminate in the various cranial blood-sinuses. 
They drain the cerebral cortex and communicate very freely 
with one another. The deep veins drain the substance of the 
brain and eventually enter the internal cerebral veins or the 
great cerebral vein (of Galen) (p. 27). 

Classification of Sensory Nerves. — Head and Sherren 
have pointed out that the afferent fibres of cerebro-spinal 
nerves may be subdivided into three groups : — (a) Those which 



122 THE NERVOUS SYSTEM 

are concerned in the perception of painful stimuli and in the 
recognition of extremes of temperature — protopathic sensibility ; 
(b) those which are concerned in the perception and localisa- 
tion of light touch and in the recognition of intermediate 
degrees of temperature — epicritic sensibility ; (c) those which 
are concerned in muscle and joint sense and in the apprecia- 
tion of deep touch — deep sensibility. The fibres which convey 
deep sensibility run in the muscular branches and those convey- 
ing joint sense are carried to their destination by the tendons. 
When a nerve is completely divided proximal to the point 
at which it gives off its first branch, the area of sensory loss 
is usually smaller than the area of known anatomical supply, 
because the areas supplied by adjoining sensory nerves over- 
lap one another to a greater or less extent. This overlapping 
is more marked in the case of protopathic and deep sensibility 
than it is in the case of epicritic sensibility. On this account, 
when a nerve, such as the median, is divided above the origin 
of its first branch, the epicritic loss is considerably in excess 
of the loss of protopathic and deep sensibility. The fact that 
the fibres conveying deep sensibility pass with the motor 
branches and run along the tendons is of great importance, 
because it explains why there is no loss of deep sensibility 
when a nerve is cut distal to the origin of its motor branches. 
In these cases, a superficial examination may fail to detect the 
existing sensory loss, and it is, therefore, necessary to examine 
for epicritic sensibility in all cases of suspected or possible 
nerve injury. It must also be observed that the division of 
tendons, with or without the division of a nerve, will usually 
lead to some impairment of deep sensibility. 

THE SPINAL NERVES 

Each spinal nerve is formed by the union of an 
anterior and a posterior nerve-root. The anterior nerve-roots 
are purely motor, and they arise from the large nerve-cells 
in the anterior column of grey matter in the spinal medulla. 



THE SPINAL NERVES 



123 



The posterior nerve-roots are purely sensory, and they enter 
the spinal medulla at the apex of the posterior column 
of grey matter. Each posterior nerve-root has a ganglion 
upon it containing cells, which send peripheral fibres into 
the nerve and central fibres into the spinal medulla, where 
they establish connexions with the higher neurones. The 
two nerve-roots unite with one another in the intervertebral 
foramen to form a spinal nerve, which divides, almost at once, 
into anterior and posterior rami (primary divisions) (Fig. 59). 




Fig. 59. — Diagram to illustrate the course taken by Sensory Fibres 
after entering the Spinal Medulla. 



A. Spino-thalamic tract (painful, thermal 

and tactile sensations). 

B. Posterior funiculus of spinal medulla 

(muscle and joint sense, and a few 
tactile fibres). 



C. Anterior nerve-root. 

D. Posterior nerve-root 

E. Anterior ramus (primary division). 

F. Posterior ramus. 

A". Typical spinal nerve. 



As the spinal medulla is much shorter than the vertebral 
canal, in which it lies, the nerve-roots in the cervical region 
are much shorter than those in the thoracic and other regions, 
and the lower part of the canal is occupied by the long nerve- 
roots of the lower lumbar, the sacral and the coccygeal 
nerves. 

Both of the rami into which each spinal nerve divides are 
mixed nerves. The posterior rami (primary divisions) are 
entirely distributed to the muscles and skin of the back of the 
trunk, neck and head. The anterior rami form the cervical, 



124 THE NERVOUS SYSTEM 

brachial, lumbar, sacral and pudendal plexuses, while, in the 
thoracic region, they constitute the intercostal nerves. 

The spinal nerves are named according to the region of the 
vertebral column at which they emerge from the vertebral 
canal. Thus there are eight cervical, twelve thoracic, five lumbar, 
five sacral and one coccygeal nerve on each side of the body. 

THE POSTERIOR RAMI (PRIMARY DIVISIONS) 

Each posterior ramus, typically, divides into lateral and 
medial branches, of which one is distributed to both skin and 
muscles, while the other supplies muscles only. 

The First Cervical Nerve sends no branches to the skin, 
but the medial branch of the second, termed the greater 
occipital nerve, ascends over the back of the scalp and supplies 
an extensive cutaneous area. It is usually aided in this dis- 
tribution by the third occipital nerve, which represents the 
medial branch of the third cervical nerve. In the occipito- 
cervical type of neuralgia, the pain is experienced over the 
area supplied by the two occipital nerves. 

The fourth, fifth and sixth cervical nerves supply the skin 
of the back of the neck above the level of the superior border 
of the scapula, but the seventh and eighth cervical nerves 
are distributed solely to muscles (Fig. 60). 

The upper thoracic nerves supply the extensor muscles of 
the vertebral column, and their cutaneous tranches supply 
horizontal bands of skin extending from the median plane to 
the posterior axillary line (Fig. 60). The lower thoracic 
nerves give off corresponding motor branches and their 
cutaneous branches become increasingly oblique, so that the 
twelfth supplies the skin over the iliac crest. 

In the upper three lumbar nerves, which have a similar 
distribution, this obliquity becomes still more marked, and 
their terminal branches supply the skin of the buttock. The 
fourth and fifth lumbar nerves do not reach the skin. 

The upper three sacral nerves give off branches to the 



THE POSTERIOR RAMI 



125 



lower part of the sacra-spinalis (erector spinae) and cutaneous 
branches to the buttock. The fourth and fifth sacral nerves 




{Photo by Alinari. 
Fig. 60. — The Areas of Skin supplied by the Posterior Rami (primary 
divisions) of the Spinal Nerves. 

Note. — The posterior rami of C. 1, 7 and 8, and L. 4 and 5, do not supply any 

branches to the skin. 

unite with the coccygeal, and the small trunk formed in this 
way supplies a limited area of skin over the coccyx. 

Referred pain from visceral disturbances is usually experi- 
enced in the areas of distribution of the anterior rami, but it 



i 2 6 THE NERVOUS SYSTEM 

may also involve the posterior rami. In cases of gastric ulcer 
or ureteral calculus, areas of cutaneous hyperalgesia are fre- 
quently to be found in the regions supplied by the posterior 
rami. Sometimes, however, the pain is not referred to the 
skin, but to the sensory nerve-endings in the muscles of the 
back, and it then gives rise to areas of muscular hyperalgesia 
which can readily be recognised, if the finger is carried down- 
wards over the sacro-spinalis (erector spina?). Gentle pressure 
is sufficient to make the patient wince in quite a characteristic 
way when the finger passes over the hyperalgesic area. 

THE ANTERIOR RAMI (PRIMARY DIVISIONS) 

The anterior rami of the upper four cervical nerves take 
part in the formation of the Cervical Plexus, which is placed 
under cover of the sterno-mastoid muscle. 

The cutaneous branches of this plexus supply a large area of 
skin, extending downwards on the trunk to the level of the 
second rib (Fig. 61), where the branches of the third and 
fourth cervical nerves overlap the branches of the second 
thoracic. The intervening nerves (C. 5-8, T. 1) do not 
appear on the surface of the trunk, as they are destined for 
the supply of the upper limb. On this account, the line of 
anaesthesia on the anterior surface of the body is the same 
for all fracture-dislocations of the vertebral column occurring 
between the fourth cervical and the first thoracic vertebras, and 
it therefore bears no relation to the site of the injury. The 
cervical plexus (C 3 and 4) is responsible for the supply of the 
skin over the acromion and over the proximal part of the 
deltoid {vide infra). 

Of the motor branches of the cervical plexus, the Phrenic 
Nerve is the most important. Most of its fibres come from 
the fourth cervical nerve, but it usually receives a few fibres 
either from the third or the fifth, in addition. The phrenic 
nerve descends through the neck, lying behind the internal 
jugular vein, and comes into intimate relation with the lower 



THE CERVICAL PLEXUS 



127 



anterior group of the deep cervical lymph glands and the 
cervical dome of the pleura. It crosses the apical pleura, 
obliquely, medially and backwards, and gains the mediastinal 
space (Fig. 122). On the left side, the phrenic nerve crosses the 




[Photo ly Alinari. 
Fig. 61. — The Nerve-supply ot the Anterior Aspect of the Trunk. 

arch of the aorta and the left side of the pericardium, before 
reaching the diaphragm, to which it is distributed. On the 
right side, the nerve descends close to the superior vena cava 
and then crosses the right side of the pericardium. It not 
only supplies the right half of the diaphragm but some of its 



128 THE NERVOUS SYSTEM 

fibres accompany the inferior vena cava into the abdomen, 
where they are distributed to the liver substance, the gall 
bladder and the bile ducts. 

As it lies in the root of the neck, the phrenic nerve may 
become embedded in the deep cervical glands when they are 
affected with tuberculous disease, or it maybe involved by 
the pleuritic thickening which usually accompanies apical 
phthisis. Under these circumstances, the contractions of the 
diaphragm may be incomplete and irregular, a condition not 
uncommon in phthisis in both its early and its later stages. 

The phrenic nerves, like all motor nerves, convey the 
afferent fibres from the muscles which they supply, and those 
fibres which the right phrenic supplies to the liver, etc., are also 
afferent. When the terminal branches of the phrenic are 
stimulated, the pain may be referred, not to the structure at 
fault but to the cutaneous distribution of the nerves from 
which the phrenic takes origin (C. 3, 4 and 5). In tropical 
abscess of the liver, 16 per cent, of cases are said to experi- 
ence pain over the right shoulder region (Fig. 61), and 
the same symptom may be noted, though less commonly, in 
diaphragmatic pleurisy and cholecystitis (see also p. 190). 

The remaining motor branches supply the prevertebral 
muscles, including the levator scapula (C. 3 and 4), and 
assist the accessory nerve to innervate the stcmo-mastoid (C. 2 
and 3) and the trapezius (C. 3 and 4). 

The upper four cervical nerves are rarely involved in 
injuries, as they are short and not liable to be stretched and 
torn. Strains of sufficient violence to injure these nerves will 
probably produce a fracture-dislocation of the cervical vertebral 
column. 

THE BRACHIAL PLEXUS 

The Brachial Plexus is formed by the anterior rami of 
the lower four cervical and the first thoracic nerves, and the 
manner in which these nerves are connected to one another is 
very constant. 



THE BRACHIAL PLEXUS 129 

The fifth and sixth cervical nerves unite to form the upper 
trunk ; the seventh cervical nerve constitutes the middle trunk, 
and the eighth cervical and first thoracic nerves unite to form 
the lower trunk. Each trunk divides into an anterior and a 
posterior division, and the three posterior divisions unite with 
one another, forming the posterior cord. The anterior divis- 
ions of the upper and middle trunks unite to form the lateral 
cord, while the anterior division of the lower trunk constitutes 
the medial cord. 

Prior to the formation of the cords, certain nerves arise 
from the plexus. They are termed the supra-clavicular 
branches and they include (1) the supra-scapular nerve, (2) the 
nerve to the subclavius, (3) the long thoracic nerve (of Bell), 
and (4) the dorsalis scapulae nerve (to the rhomboids). 

The remaining branches of the brachial plexus arise from 
the three cords. The lateral cord gives off (1) the lateral 
anterior thoracic nerve, (2) the musculo-cutaneous nerve, and 
(3) the lateral head of the median nerve. 

The posterior cord gives off (1) the upper subscapular nerve, 
(2) the thoraco-dorsal (middle or long subscapular nerve), (3) 
the lower subscapular nerve, (4) the axillary (circumflex) nerve, 
and (5) the radial (musculo-spiral) nerve. 

The medial cord gives off (1) the medial anterior thoracic 
nerve, (2) the medial cutaneous nerve of the arm (lesser in- 
ternal cutaneous), (3) the medial cutaneous nerve of the 
forearm (internal cutaneous), (4) the medial head of the 
median nerve, and (5) the ulnar nerve. 

It is necessary to describe not only the distribution of each 
individual branch of the plexus but also the destination of the 
individual spinal nerves which form the plexus, because lesions 
of the spinal medulla or of the spinal nerves produce effects 
which may involve several nerves, some of them only partially, 
whereas lesions of individual branches are necessarily confined 
to those branches, although affecting the areas supplied by 
more than one spinal nerve {vide infra). 



13° 



THE NERVOUS SYSTEM 










Fig. 62. — Diagram to show the branches and the mode of formation of the 
Cervical and the Brachial Plexuses. (Turner's Anatomy.) 

CI. Line of clavicle. 



L. Lateral cord. 
L.T. Lower trunk. 
M. Medial cord. 
M. T. Middle trunk. 
P. Posterior cord. 
5". Sympathetic trunk. 
U. T. Upper trunk. 

a. Axillary (circumflex) nerve. 
c . Grey ramus communicans. 
c.c. Nervus cutaneus colli. 
d.s. Dorsalis scapula; nerve (to rhom- 
boids). 
g.a. Great auricular nerve. 
/. Nerve to levator scapulae. 
l.o. Lesser occipital nerve. 
l.a.t. Lateral anterior thoracic nerve. 



l.t. Long thoracic nerve (of Bell). 
in. Median nerve. 
m.cl.c. Medial cutaneous nerve of fore- 
arm. 
m.b.c. Medial cutaneous nerve of arm. 
in. a. t. Medial anterior thoracic nerve. 
inc. Musculocutaneous nerve. 
p. Phrenic nerve. 
r. Radial (musculo-spiral) nerve. 
r.d.c. Ramus descendens cervicalis. 
j. Subscapular nerve. 
sc. Supraclavicular nerves. 
jj. Suprascapular nerve. 
/. Nerve to trapezius. 
t.d. Thoraco-dorsal (long subscapular) 
nerve. 
11. Ulnar nerve. 






THE BRACHIAL PLEXUS 131 

The Supra-clavicular Branches of the Brachial 

Plexus 

1. The Supra-scapular nerve (C. 5 and 6) supplies the supra- 
and the infra-spinatus muscles. 

The supra-spinaUis arises from the supra-spinous fossa of the scapula 
and runs laterally above the capsule of the shoulder-joint to be inserted 
into the greater tubercle of the humerus. It initiates the movement of 
abduction at the shoulder-joint and helps the deltoid to maintain the limb 
in that position. The bulk of the muscle is hidden by the insertion of the 
trapezius, but when the supra-spinatus becomes atrophied there is some 
hollowing out above the spine of the scapula. 

The infra-spinatus arises from the large infra-spinous fossa of the scapula 
and runs laterally, posterior to the capsule of the shoulder-joint, to be 
inserted into the greater tubercle of the humerus. It is a powerful lateral 
rotator, and it assists in the movements of adduction and extension. The 
infra -spinatus is partly overlapped by the deltoid, the trapezius and the 
latissimus dorsi, but, when it is atrophied, the dorsal surface of the scapula 
can readily be palpated through the skin above the inferior angle, as the 
muscle is only covered by fascice in that situation. 

Lesions of the supra-scapular nerve are by no means 
common. They result in weakening of the movements of 
abduction and lateral rotation at the shoulder, but as the 
deltoid and the teres minor are not involved, the disability 
is not very marked. In many cases the movement of abduc- 
tion cannot be initiated, but, if passively commenced, it can be 
continued and maintained. No sensory changes accompany 
complete paralysis of the supra-scapular nerve. 

2. The Nerve to the Subclavius (C. 5 and 6) is of little 
practical importance. The subclavius, which extends from 
the inferior aspect of the clavicle to the sternal end of the 
first rib, helps to steady the clavicle during movements at 
the shoulder-joint. Paralysis of this muscle produces little 
disability. 

3. The Dorsalis Scapulae Nerve (C. 5) arises from the 
anterior ramus of C 5 before the latter joins C. 6 to form the 
upper trunk of the plexus. The nerve crosses the floor of 



132 THE NERVOUS SYSTEM 

the posterior triangle of the neck and runs along the vertebral 
border of the scapula to supply the rhomboids, major and 
minor. 

These two muscles arise from the spines of the upper 
thoracic and lower cervical vertebrae, and pass downwards and 
laterally to be inserted into the vertebral' border of the 
scapula. When they contract, they draw the scapula upwards 
and medially, thus helping to brace back the shoulders. 
In paralysis of the rhomboids, the weight of the upper limb 
draws the scapula downwards and, as the lower part of the 
serratus anterior is unopposed, the inferior angle is tilted in a 
lateral direction. The condition is determined by a careful 
comparison of the relative positions of the two scapulae. 

4. The Long Thoracic Nerve (of Bell) arises by three roots, 
which spring from the fifth, sixth and seventh cervical nerves, 
before the formation of the trunks of the brachial plexus. 
It enters the axilla and descends on the medial wall to supply 
the serratus anterior. 

The Serratus Anterior arises from the upper eight ribs, a 
little in front of the mid-axillary line, and its fibres pass 
backwards, round the chest wall and closely applied to it, to 
be inserted into the ventral aspect of the vertebral border of 
the scapula. When the muscle contracts, it draws the scapula 
forwards and laterally and, at the same time, it rotates it 
clockwise (as seen from in front). 

Movements of flexion and abduction at the shoulder-joint 
itself are limited to 90 , and, although these movements can 
apparently be carried out to an angle of about 160 , the 
additional range is obtained by movements of the shoulder- 
girdle as a whole. This additional movement is produced 
mainly by the serratus anterior and the trapezius. 

The serratus anterior plays an important part in forward 
pushing movements, but it is aided by the trapezius and the 
rhomboids, which help to steady the scapula. When the 
long thoracic nerve is injured alone, the patient cannot 
flex his arm beyond a right angle, and if the arm is passively 



THE BRACHIAL PLEXUS 133 

flexed beyond that angle, the patient is unable to perform any 
forward pushing movements. Under these conditions, his 
endeavours result in marked "winging" of the scapula. On 
the other hand, forward pushing movements with the arm 
flexed to less than a right angle are not only possible, but 
they do not produce any "winging" of the scapula, which is 
steadied by the trapezius and the rhomboids (Sherren). 

If, however, either or both of the latter muscles are paralysed 
in addition to the serratus anterior, forward pushing move- 
ments carried out in any plane cause " winging " of the 
scapula. The combined lesion appears to be the less un- 
common condition. 

When the scapula is fixed by the contraction of the 
trapezius and the rhomboids, the serratus anterior can help 
inspiration by elevating the upper eight ribs. Patients suffering 
from chronic bronchitis and emphysema bring into use all the 
auxiliary muscles of respiration when they are seized by a fit 
of coughing, and the digitations of the serratus anterior stand 
out in relief on the medial wall of the axilla, more especially 
in spare subjects. 

The Infraclavicular Branches of the Brachial 

Plexus 

(A) Lateral Cord. — The Lateral Anterior Thoracic Nerve 
(C. 5, 6 and 7) supplies the whole of the clavicular head and 
part of the costo-sternal head of the pectoralis major. 

The pectoralis major covers the upper part of the anterior 
chest wall, and its lower border constitutes the anterior 
axillary fold. In the female, it is partly obscured by the 
mammary gland. From its origin the muscle passes laterally 
to be inserted into the proximal part of the humerus. Its 
line of pull lies below and anterior to the centre of the 
shoulder-joint, and the muscle therefore acts as a flexor, 
adductor and medial rotator of the arm. 

Paralysis of the pectoralis major occurs along with paralysis 
of other muscles in injuries of the upper trunk of the brachial 



134 THE NERVOUS SYSTEM 

plexus and in lesions of the spinal medulla, etc., but as an 
isolated condition it is practically unknown. 

The costo-sternal head may be removed in the complete 
operation for scirrhus mammae or it may be absent congenitally 
without causing any noticeable disability. When this part of 
the muscle is absent congenitally, there is visible deformity 
and the chest appears to be much flatter on the affected side. 
The condition, however, does not necessarily predispose to 
phthisis, and the patient may have an otherwise normal and 
healthy chest. 

The Musculocutaneous Nerve (C. 5, 6 and 7) contains 
both motor and sensory fibres. Its motor branches supply 
the coraco-brachialis, the biceps and the brachialis (b. anticus) 
muscles. 

The Coraco-brachialis can be seen and felt on the lateral wall of the 
axilla, when the arm is fully abducted. It arises from the tip of the 
coracoid process and is inserted into the middle of the medial aspect of 
the shaft of the humerus. Its line of pull lies anterior and a little medial 
to the centre of the shoulder-joint, and the muscle therefore acts as a flexor, 
adductor and medial rotator of the arm. 

The Biceps arises from the tip of the coracoid process and from the 
upper border of the glenoid cavity. As it passes to be inserted into the 
radial tuberosity, it forms a well-marked elevation on the front of the arm. 
The biceps is a powerful flexor and supinator of the forearm and it also 
acts as a weak flexor of the shoulder joint. 

The Brachialis lies behind the lower part of the biceps. It arises from 
the anterior aspect of the humerus and is inserted into the coronoid process 
of the ulna. It is a powerful flexor of the elbow-joint, but it does not 
depend for its nerve-supply on the musculo-cutaneous nerve alone, as it 
also receives a branch from the radial (musculo-spiral) nerve. 

The motor symptoms in paralysis of the musculo-cutaneous 
nerve are great weakness in the movement of flexion at the 
elbow and impairment in the power of supination, which is 
normally a much stronger movement than pronation. 

The sensory part of the musculocutaneous nerve 
constitutes the lateral cutaneous nerve of the forearm. 
It divides into volar [anterior) and dorsal branches, which 
supply the corresponding surfaces of the lateral aspect of the 



THE BRACHIAL PLEXUS 



135 



forearm, from the elbow to the wrist. These two branches 
overlap one another to such an extent that section of one of 
them alone produces no discoverable alteration in the 




A E 

FlG. 63. — The Nerve-supply of the Skin on the Anterior Aspect 
of the Upper Limb. 

A. The individual nerves of supply. 

B. The segmental supply. 



1. Posterior supraclavicular nerves. 

2. Lateral cutaneous nerve of arm. 

3. Dorsal cutaneous nerve of forearm. 

4. Lateral cutaneous nerve of forearm. 

5. Palmar branch of radial nerve. 

6. Digital branches of median nerve. 



7. Digital branches of ulnar nerve. 

8. Palmar branch of ulnar nerve. 

9. Palmar branch of median nerve. 

10. Medial cutaneous nerve of forearm. 

11. Medial cutaneous nerve of arm. 

12. Intercosto-brachial nerve. 



sensibility of the limb. Further, the dorsal branch overlaps 
the dorsal cutaneous nerve of the forearm (lower external 
cutaneous branch of the musculo-spiral nerve), but the volar 
branch does not overlap the volar branch of the medial 



136 THE NERVOUS SYSTEM 

cutaneous nerve of the forearm to any extent. As a result, 
when the whole of the musculocutaneous nerve is paralysed, 
the sensory disturbance is very ill-defined on the back of the 
forearm, whereas, on the front of the forearm, a fairly sharp 
line of demarcation can always be found. 

The lateral head of the median will be considered along 
with the medial head (p. 149). 

(B) The Posterior Cord (C. 5, 6, 7, 8 and T. 1)— The 
Upper Subscapular Nerve (C 5 and 6) is entirely distributed 
to the subscapularis, which forms the proximal part of the 
posterior wall of the axilla. 

The subscapularis arises from the ventral surface of the scapula, crosses 
the anterior aspect of the capsule of the shoulder-joint, and is inserted into 
the lesser tubercle of the humerus. It acts as a medial rotator and assists 
in flexion and adduction of the humerus. Section of the upper subscapular 
nerve produces little motor disability, but, as the muscle atrophies, the 
anterior aspect of the capsule of the shoulder-joint becomes seriously 
weakened, and this condition predisposes to dislocation. 

The Lower Subscapular Nerve supplies a few twigs to the subscapul- 
aris, but is mainly distributed to the teres major. This muscle arises 
from the dorsal aspect of the inferior angle of the scapula and passes 
upwards and laterally on the posterior wall of the axilla to be inserted 
into the floor of the intertubercular sulcus (bicipital groove). It acts as a 
medial rotator, adductor and extensor of the humerus. Section of the 
lower subscapular nerve produces no discoverable disability, as the 
latissimus dorsi has a precisely similar action to that of the teres major. 

The Thoracodorsal (Long Subscapular) Nerve supplies the 
latissimus dorsi muscle, which is mainly responsible for the 
formation of the posterior axillary fold. This muscle has a 
wide origin in the lower part of the back, and it narrows as it 
passes to its insertion into the medial lip of the intertubercular 
sulcus (bicipital groove). When both the thoraco-dorsal and 
the lower subscapular nerves are paralysed, the movement of 
extension at the shoulder-joint is extremely weak, as it is then 
performed almost entirely by the posterior fibres of the 
deltoid, since the infra-spinatus and the teres minor do not 
act at good mechanical advantage. The posterior fold of the 



THE BRACHIAL PLEXUS 137 

axilla loses its bulk as the muscles atrophy, and the axillary 
border of the scapula can then be palpated without difficulty. 

The Axillary (Circumflex) Nerve arises from the posterior 
cord in the axilla, where it lies behind the third part of the 
axillary artery. After passing through the quadrilateral space, 
it winds round the posterior aspect of the surgical neck of the 
humerus and so reaches the deep surface of the deltoid. It 
contains both motor and sensory fibres. The former are 
distributed to the deltoid and the teres minor. 

The Deltoid arises from the anterior border of the lateral 
third of the clavicle, the tip and lateral border of the acromion 
and the lower border of the spine of the scapula. From this 
wide origin the fibres pass distally and converge to be inserted 
into the middle of the lateral surface of the shaft of the 
humerus. The anterior fibres aid in the movements of flexion 
and medial rotation, while the posterior fibres take part in the 
opposite movements. Acting as a whole, the deltoid is a 
powerful abductor of the humerus, and, in this movement, it 
is aided only by the supra-spinatus (p. 131). 

The teres minor lies along the lateral border of the infra-spinatus, and it 
performs the same actions as that muscle, i.e. it laterally rotates, adducts 
and extends the humerus. 

JVhen the axillary nerve is paralysed, abduction of the 
humerus is the only movement which is markedly affected. 
A certain degree of this movement, however, is still possible, 
as the supra-spinatus is not involved, and, further, the latter 
muscle is assisted by the serratus anterior, which acts through 
the shoulder-girdle. Atrophy of the deltoid is easy to determine. 
The deltoid covers the greater tubercle of the humerus and, 
in this way, it gives the shoulder its normal rounded appear- 
ance. In atrophy of the muscle, the lateral border of the 
acromion becomes more distinct and the shoulder loses its 
normal contour. The tubercles are easy to palpate and the 
coracoid process, which is normally covered by the anterior 
fibres of the muscle, may cause a surface elevation below the 
junction of the intermediate and lateral thirds of the clavicle. 



i 3 8 THE NERVOUS SYSTEM 

The cutaneous branches of the axillary nerve supply the skin 
over the distal two-thirds of the deltoid. They are slightly 
overlapped, proximally by the posterior supra-clavicular (supra- 
acromial) nerves (C. 3 and 4) and distally by the dorsal 
cutaneous branch of the radial nerve (upper external cutaneous 
branch of the musculo-spiral nerve) (Fig. 6.3). In complete 
paralysis of the axillary nerve, the skin over the distal two- 
thirds of the deltoid shows loss of both epicritic and protopathic 
sensibility. The combination of the motor and sensory pheno- 
mena renders paralysis of this nerve easy to determine. 

The Radial (Musculo-spiral) Nerve arises from the posterior 
cord in the axilla and descends behind the artery. In this 
part of its course it lies medial to the proximal part of the 
shaft of the humerus, against which it is compressed in " crutch " 
and " Saturday night " paralyses. A short distance beyond 
the posterior fold of the axilla, it passes distally and laterally 
across the posterior aspect of the humerus in the radial groove. 
At the distal extremity of the groove, the nerve re-enters the 
anterior compartment of the arm and, in front of the lateral epi- 
condyle of the humerus, it ends by dividing into superficial and 
deep branches (o.T. radial and posterior interosseous nerves). 

The radial nerve can be rolled against the lateral aspect of 
the humerus as it pierces the lateral intermuscular septum. 
This point corresponds to the junction of the middle and 
proximal thirds of the line joining the insertion of the deltoid 
to the tip of the lateral epicondyle. Proximal to that point, 
the radial nerve may be rolled against the floor of the radial 
groove on deep pressure through the triceps. 

As the radial (musculo-spiral) nerve passes through the axilla, 
it gives off a cutaneous branch, which supplies the skin on the 
dorsum of the arm (Fig. 64), and motor branches to the long 
and medial heads of the triceps. In the radial groove, the 
nerve supplies branches to all three heads of the triceps and to 
the anconeus. At the distal extremity of the groove it gives 
off the dorsal cutaneous nerve of the forearm. This branch 
breaks up into proximal and distal divisions (upper and lower 



THE BRACHIAL PLEXUS 



i39 



external cutaneous branches of musculo-spiral), which supply 
the antero-lateral aspect of the arm and the middle part of the 




Fig. 64. — The Nerve-supply of the Skin on the Dorsal Aspect 
of the Upper Limb. 

A. The segmental supply. 

B. The individual nerves of supply. 



1. Posterior supra-clavicular nerves. 

2. Lateral cutaneous nerve of arm. 

j, 4. Dorsal cutaneous nerve of forearm 
(upper and lower external cutane- 
ous branches of musculo-spiral 
nerve). 

5. Lateral cutaneous nerve of forearm. 

6. Superficial division of radial nerve. 



7. Dorsal cutaneous branch of ulna! 

nerve. 

8. Medial cutaneous nerve of forearm 

(internal cutaneous nerve). 

9. Intercosto-brachial nerve. 

10. Posterior cutaneous nerve of arm (in- 
ternal cutaneous branch of musculo- 
spiral nerve). 



dorsum of the forearm, respectively (Fig. 64). After piercing 
the lateral intermuscular septum and re-entering the anterior 
compartment of the arm, the radial (musculo-spiral) nerve sends 



i 4 o THE NERVOUS SYSTEM 

branches to the brachio-radialis (supinator longus), the extensor 
carpi radialis longus and the brachialis (p. 134). 

The Triceps arises by three heads. The long head arises from the upper 
part of the axillary border of the scapula and it can be palpated distal to 
the posterior fold of the axilla, when the forearm is actively extended. The 
lateral and medial heads arise from the posterior aspect of the humerus. 
When the lateral head contracts, it forms an oblique ridge on the back of 
the arm, just below the posterior border of the deltoid. 

The triceps is inserted into the proximal surface of the olecranon, and 
acts as a powerful extensor of the elbow. In this action it is aided by 
the anconeus, a small muscle which passes from the posterior aspect of the 
lateral epicondyle of the humerus to the lateral aspect of the olecranon. 

The Brachio-radialis is an extremely important muscle in many ways. 
It arises from the lateral intermuscular septum and the lateral epicondylic 
ridge of the humerus, and is inserted into the lateral aspect of the radius, 
just proximal to the styloid process. Its principal action is flexion of the 
elbow, and when that movement is attempted against resistance, the brachio- 
radialis forms an unmistakable prominence on the lateral part of the front 
of the forearm. When the limb is supine, the line of the pull of the 
brachio-radialis lies medial to the axis of the movement of pronation, and 
therefore the muscle acts as a pronator, in the initial stage of pronation. 
But, in the mid-prone position, the line of pull exactly overlies the axis 
of movement and the muscle ceases to act as a pronator. When the limb 
is fully pronated, the line of pull lies lateral to the axis of movement, 
and the brachio-radialis, therefore, may act as a supinator until the mid- 
prone position is reached. 

The brachio-radialis is paralysed when the radial (musculo-spiral) nerve 
is injured in the radial groove or in the axilla, but it is not affected in the 
" wrist-drop" paralysis of lead-poisoning. 

The Extensor Carpi Radialis Longus lies under cover of the brachio- 
radialis. It arises from the humerus and the lateral intermuscular septum just 
distal to that muscle and is inserted into the dorsum of the base of the second 
metacarpal bone. It is a powerful extensor of the wrist-joint and, when 
the forearm is pronated, it assists in flexion of the elbow-joint. Like the 
brachio-radialis, it commonly escapes in lead-poisoning, but as the other carpal 
extensors are involved its action may be masked by the tonus of the carpal 
flexors when an endeavour is made to extend the wrist. If, however, the 
hand is supported during the movement, the contraction of the extensor carpi 
radialis longus can be satisfactorily demonstrated. 

The actions and attachments of the Brachialis are described on page 134. 

The Deep Branch of the Eadial Nerve supplies the sufin- 



THE BRACHIAL PLEXUS 141 

ator (brevis) and is thereafter termed the Dorsal Interosseous 
Nerve. It winds round the proximal part of the radius and 
gains the posterior compartment of the forearm. It supplies 
alb the extensor muscles of the fingers and wrist, except the 
extensor carpi radialis longus. 

When the dorsal aspect of the forearm is examined, a dis- 
tinct longitudinal groove is seen slightly to the ulnar side 
of the middle line. When this groove is palpated, it is found 
to correspond to the subcutaneous dorsal border of the ulna. 
The extensor muscles lie to the radial side of the groove, and 
the mass which lies to its ulnar side is formed by the flexor 
digitorum profundus and the flexor carpi ulnaris. 

The group of muscles supplied by the dorsal interosseous 
nerve includes the extensor carpi radialis brevis, the extensor 
carpi ulnaris, the extensor digitorum communis, the extensor 
digit i quinti proprius, the extensor indicis proprius, the abductor 
pollicis longus, the exte?isor pollicis longus and brevis. 

The Superficial Branch of the Radial Nerve (o.t. Radial) 
is purely sensory. It supplies branches to the skin (t) of the 
thenar eminence, (2) of the radial part of the dorsum of the hand, 
(3) of the dorsal aspects of the lateral three and a half digits, 
except over the distal and part of the middle phalanx. It 
must be remembered that this nerve establishes connexions 
with (1) the lateral cutaneous nerve of the forearm (p. 134), 
(2) the dorsal cutaneous nerve of the forearm (p. 138) 
and (3) the dorsal branch of the ulnar nerve. On this 
account, division of the superficial branch of the radial nerve 
produces no appreciable alteration in the sensibility of the skin 
areas which it supplies (Sherren). 

Radial (Musculo-spiral) Paralysis. — Complete division 
of the radial nerve before any of its branches are given off results 
in widespread motor paralysis, but the sensory loss is relatively 
insignificant. The triceps and anconeus are paralysed, and, 
therefore, active extension of the elbow is impossible and the 
joint is maintained in a semi-flexed attitude by the tonus of 
the flexors of the forearm. The paralysis of the brachio- 



142 THE NERVOUS SYSTEM 

radialis does not produce any special attitude, but, as all the 
extensors of the wrist and fingers are involved, the wrist and 
fingers are maintained in a position of flexion by the tonus of 
their flexor muscles. At the same time, it should be remem- 
bered that the lumbricals and interossei (p. 145) are able to 
extend the interphalangeal joints of the medial four digits, and 
care must be taken not to assume that such a movement, 
occurring during an endeavour to extend the fingers and wrist, 
is produced by the extensor muscles. 

■\Yhen the radial (musculo-spiral) nerve is divided distal to 
the point of origin of the dorsal cutaneous nerve of the fore- 
arm, there is no appreciable loss of sensibility in the forearm 
or hand, on account of the communications which exist between 
the superficial branch and the adjoining nerves (p. 141). If 
the radial nerve is divided proximal to the point of origin 
of the dorsal cutaneous nerve of the forearm, the sensory loss 
involves the radial side of the dorsum of the hand. The fore- 
arm is not affected, owing to the overlapping of the dorsal 
cutaneous nerve by the lateral and medial cutaneous nerves of 
the forearm. • Both epicritic and protopathic sensibilities are 
lost over the radial half of the dorsum of the hand and over 
the dorsal aspect of the first phalanx of the thumb, but, owing 
to overlapping by the volar (palmar) digital nerves, the second, 
third and fourth digits are not affected. 

The superficial branch of the radial nerve establishes its 
communications in the distal third of the forearm, and, when 
it is injured in this part of its course, some loss of sensibility 
may be discovered on the dorsum of the hand. 

(C) The Medial Cord (C 8 and T. 1).— The Medial 
Anterior Thoracic Nerve supplies the pectoralis minor and 
assists the lateral anterior thoracic nerve to supply the 
pectoralis major (p. 133). 

The pectoralis minor lies under cover of the major and 
extends from the sternal ends of the third, fourth and fifth ribs 
to the coracoid process of the scapula. When it contracts, it 
draws the point of the shoulder downwards and forwards ; or, 



THE BRACHIAL PLEXUS 



'4: 



if the scapula is fixed, it can act as an auxiliary muscle of 
respiration. It is never paralysed alone. 

The Medial Cutaneous Nerve of the Arm (Lesser Internal 




Fig. 65.- 



-The Nerve-supply of the Skin on the Anterior Aspect 
of the Upper Limb. 



1. Posterior supraclavicular nerves. 

2. Lateral cutaneous nerve of arm. 

3. Dorsal cutaneous nerve of forearm. 

4. Lateral cutaneous nerve of forearm. 

5. Palmar branch of radial nerve. 

6. Digital branches of median nerve. 



A. The individual nerves of supply. 

B. The segmental supply. 

7. Digital branches of ulnar nerve. 

8. Palmar branch of ulnar nerve. 

9. Palmar branch of median nerve. 

10. Medial cutaneous nerve of forearm. 

11. Medial cutaneous nerve of arm. 

12. Intercosto-brachial nerve. 



Cutaneous) communicates with the intercosto-brachial (inter- 
costo-humeral, T. 2) and then supplies the skin on the dorso- 
medial aspect of the arm. In angina pectoris (p. 192) and, 
sometimes, in malignant disease of the breast referred pain is 



144 THE NERVOUS SYSTEM 

experienced in the area supplied by this nerve. In the latter 
case, the condition may be caused by direct pressure on the 
nerve by enlarged lymph glands in the axilla. 

The Medial Cutaneous Nerve of the Forearm (Internal 
Cutaneous) (C. 8 and T. i) pierces the deep fascia about 
half-way down the arm, and divides into volar (anterior) and 
ulnar (posterior) branches. These two branches are respons- 
ible for the supply of the skin over the medial half of the 
forearm, and, although they overlap one another with great 
freedom, they do not overlap the adjoining nerves to the 
same extent. As a result, when either branch is divided 
alone, the sensory loss is sharply demarcated on the radial 
side, but it disappears very gradually on the ulnar side. The 
area supplied by this nerve may be involved in the referred 
pain of angina pectoris (p. 192). 

The Ulnar Nerve (C. S and T 1) arises from the medial 
cord of the plexus in the axilla, and is placed on the medial 
side of the brachial artery in the proximal part of the arm. 
In the distal part of the arm it leaves the anterior compart- 
ment and passes behind the medial epicondyle of the humerus. 
In this situation the nerve is only covered by skin and fascia?, 
and, as it is in direct contact with the bone, it is consequently 
exposed to injury. 

At the elboiv, the ulnar nerve supplies branches to the flexor 
carpi ulnaris and to the part of the flexor digitorum profundus 
which acts on the ring and little fingers. 

Its course through the forearm corresponds to a line drawn 
from the medial epicondyle to the lateral side of the pisiform 
bone, which can easily be felt on the ulnar side of the wrist at 
the proximal border of the hypothenar eminence. Proximally 
it is covered by the fleshy belly of the flexor carpi ulnaris, but 
near the wrist it becomes superficial and lies on the lateral 
side of the tendon of that muscle. 

The Flexor Carpi Ulnaris arises both from the medial epicondyle and 
from the medial side of the olecranon. It descends on the ulnar side of 
the forearm, and its tendon can be traced to its insertion into the pisiform 



THE BRACHIAL PLEXUS 145 

bone. Under ordinary conditions, the muscle acts along with the other 
flexors of the wrist, but, when it contracts alone, it produces ulnar de- 
viation of the hand in addition to flexion of the wrist. Ulnar deviation of 
the hand, without either flexion or extension, is produced by the simul- 
taneous contraction of the flexor carpi ulnaris and the extensor carpi 
ulnaris. Inability to carry out this movement must indicate paralysis or 
parcesis of one or other of these muscles. 

In the distal part of the forearm the ulnar nerve gives 
off a volar {palmar) cutaneous branch, which supplies the skin 
over the hypothenar eminence, and a dorsal cutaneous branch, 
which supplies the ulnar side of the dorsum of the hand and 
the proximal parts of the dorsal aspects of the little finger and 
the ulnar side of the ring finger. 

In the hand, the ulnar nerve terminates by dividing into 
superficial and deep branches. The superficial branch 
supplies the skin on the volar aspect of the little finger and 
the ulnar side of the ring finger. In addition, it supplies 
the distal parts of the dorsal aspects of the same two digits. 

The Deep Branch of the Ulnar Nerve gives off no cutaneous 
branches, but it supplies the muscles of the hypothenar 
eminence, all the interossei, the medial two lumbricals and the 
adductor pollicis. 

The muscles which constitute the hypothenar eminence com- 
prise the abductor, the opponens and the flexor brevis digiti 
quinti. The actions of these muscles are indicated by their 
names, but, under normal conditions', the little finger possesses 
little power of opposition, as the ligaments of the joint between 
the fifth metacarpal bone and the hamate (unciform) bone allow 
very little rotatory movement. 

Atrophy of this group of muscles is easily recognised. It 
occurs in lesions (1) of the ulnar nerve, (2) of the lower trunk 
of the brachial plexus, e.g. Klumpke's paralysis, or following 
pressure by a cervical rib, and (3) of the lower part of the 
cervical enlargement of the spinal medulla, e.g. progressive 
muscular atrophy. 

The Lumbricals are four small muscles which arise from the 
10 



146 



THE NERVOUS SYSTEM 



tendons of the flexor digitorum profundus. They are inserted 
into the radial side of the base of the proximal phalanx of each 
of the medial four digits. In addition, their tendons are attached 
to the expansion of the extensor tendons, which covers the 
dorsal aspect of the proximal phalanx. By virtue of their 
bony insertions, these muscles act as flexors'of the metacarpo- 
phalangeal joints, but by virtue of their connexion with the 
extensor expansion they extend the two interphalangeal joints 
at the same time {vide infra). The lumbricals for the little 
and ring fingers are supplied by the deep branch of the ulnar 




Fig. 66. — Tendons attached to a Finger. (Turner's Anatomy.) 



a. Extensor digitorum communis. 

b. Flexor digitorum profundus. 

c. Flexor digitorum sublimis. 



d. Lumbrical muscle. 

e. Dorsal interosseous muscle. 

f. Dorsal expansion of extensor tendon. 



nerve, but the lateral two lumbricals are innervated by the 
median (p. 152). 

The Volar {Palmar) Interossei are three in number, and they 
act on the index, ring and little fingers. Each arises from the 
volar aspect of the metacarpal bone of the finger on which it 
acts, and each is inserted into the dorsum of the base of the 
proximal phalanx and the extensor expansion. The volar 
interossei for the ring and little fingers are inserted on the 
radial sides of their respective phalanges, but that for the index 
finger is inserted on the ulnar side. 

When the volar interossei contract, they adduct the index, 
ring and little fingers to the middle finger. In addition, they 
flex the metacarpophalangeal joints, while extending the inter- 
phalangeal joints (cf. Lumbricals). 



THE BRACHIAL PLEXUS 147 

The Dorsal Interossei act as abductors of the index, middle 
and ring fingers. The first dorsal interosseous arises from the 
adjacent sides of the first and second metacarpal bones, and 
is inserted into the radial side of the dorsum of the base of 
the proximal phalanx of the index finger. When the thumb is 
adducted, the first dorsal interosseous muscle produces a 
swelling on the dorsum of the hand between the first and 
second metacarpal bones, and it can be felt to contract during 
abduction of the index. Atrophy of this muscle occurs at an 
early stage in progressive muscular atrophy. 

The second and third dorsal interossei occupy the spaces 
between the second and third, and third and fourth metacarpal 
bones, respectively. The former is inserted into the radial side 
and the latter into the ulnar side of the first phalanx of the 
middle finger. They abduct the middle finger to the radial 
and ulnar sides respectively. 

The fourth dorsal interosseous muscle occupies the space 
between the fourth and fifth metacarpal bones, and is inserted 
into the ulnar side of the dorsum of the base of the proximal 
phalanx of the ring finger. 

When the dorsal interossei become atrophied, hollows 
appear on the dorsum of the hand between the metacarpal 
bones, and the latter can not only be palpated but may even 
be gripped between the examining finger and thumb. 

The Adductor Pollicis possesses a wide origin from the 
volar aspect of the carpus and the third metacarpal bone, 
and it is inserted into the ulnar side of the base of the 
proximal phalanx of the thumb. In studying the movement 
of adduction of the thumb, it must be remembered that the 
first metacarpal bone is so placed that what is usually de- 
scribed as its dorsal surface is, in reality, directed laterally, 
when the supine hand is by the side. Adduction of the 
thumb brings the ulnar border of the first metacarpal towards 
the radial side of the second metacarpal, and the movement 
occurs in an antero-posterior plane, provided that the hand 
is supine and by the side, as in the erect attitude. Abduction 



148 THE NERVOUS SYSTEM 

of the thumb, which is the reverse movement, must also occui 
in this plane (see also p. 151). 

When the ulnar nerve is divided near the wrist, all the 
intrinsic muscles of the hand are paralysed, with the exception 
of those supplied by the median nerve (p. 151). Owing to the 
paralysis of the interossei, the movements' of abduction and 
adduction of the fingers are lost, but not necessarily entirely so 
as their actions may be simulated by the extensor digitorum 
communis, which, however, can only act when the fingers are 
extended. At the same time it must be remembered that, mainly 
owing to the arrangement of the collateral ligaments of the 
metacarpo-phalangeal joints, free abduction and adduction of the 
fingers can only be carried out when the joints are in a position 
of extension. Abduction of the little finger and adduction of 
the thumb are impossible, although the latter movement may 
be simulated by the flexor pollicis longus and brevis. 

The fingers adopt a characteristic attitude. Owing to the 
paralysis of their interossei, the index and middle fingers are 
extended at the metacarpo-phalangeal joints and the ring and 
little fingers adopt a greater degree of the same attitude, as 
their lumbrical muscles are also paralysed. Hyperextension 
of the ring and little fingers at the metacarpo-phalangeal joints 
stretches the tendons of the flexor digitorum sublimis and 
profundus, which contract and flex the interphalangeal joints. 
The degree of flexion present in the interphalangeal joints of 
the index and middle fingers is much less, as their lumbrical 
muscles are able to oppose the action. 

The sensory loss depends on the site of the injury. If it 
occurs proximal to the origin of the dorsal cutaneous branch, 
the sensory loss involves the ulnar halves of both dorsal and 
volar aspects of the hand, the whole of the little finger and 
the ulnar half of the ring finger. Unless the injury which 
divided the nerve has also divided some of the tendons, there 
is no loss of sensibility to deep pressure. Epicritic sensibility 
is lost over the whole of the area indicated, but the area of 
protopathic loss is much smaller (see p. 121). 



THE BRACHIAL PLEXUS 149 

When the ulnar nerve is injured distal to the origin of its 
dorsal cutaneous branch, only the distal phalanges of the little 
and ring fingers are affected on the dorsal aspect of the hand. 
On the volar aspect, the loss of epicritic sensibility is the 
same as in the former case, but protopathic loss only affects 
the little finger. 

When the ulnar nerve is injured at or proximal to the elbow, 
the motor symptoms which have already been described are 
increased by the paralysis of the flexor carpi ulnaris and the 
ulnar half of the flexor digitorum profundus. As a result, 
flexion of the wrist is weakened and, when that movement is 
actively performed, the hand becomes deviated to the radial 
side. It might appear as if paralysis of the ulnar portion of 
the flexor digitorum profundus would result in hyperextension 
of the distal interphalangeal joints, but, as there is only one 
extensor muscle for all the joints of the fingers, the distal 
joints cannot be extended when the proximal interphalangeal 
joints are flexed. The attitude of the fingers, therefore, is not 
altered by the additional paralysis, and the characteristic 
main en griffe is present, as in the case of injury to the 
nerve proximal to the wrist. 

The sensory loss is very similar to that found when the 
ulnar nerve is divided proximal to the point of origin of its 
dorsal cutaneous branch, with the important difference that 
deep sensibility is lost over an area, which corresponds more 
or less accurately to the area of protopathic loss. 

The Median Nerve (C. 5, 6, 7, 8 and T. 1) is formed in 
the axilla by the union of a lateral head, derived from the 
lateral cord, with a medial head, derived from the medial 
cord. In the axilla and the arm, the median nerve is closely 
related to the great vessels and it gives off no branches 
until it supplies the superficial group of muscles of the 
forearm. These branches arise just proximal to the elbow 
and they are distributed to the pronator teres, the flexor 
carpi radialis, the palmaris longus and the flexor digitorum 
sublimis. 



150 THE NERVOUS SYSTEM 

All these muscles arise from a common origin on the medial epicondyle 
of the humerus. The Pronator Teres passes distally and laterally to be 
inserted into the middle of the lateral aspect of the radius. It acts 
as a powerful pronator and as a weak flexor of the forearm. It can 
be recognised since it forms the medial boundary of the depression which 
appears in front of the elbow, when the pronated forearm is flexed against 
resistance. 

The Flexor Carpi Radialis passes somewhat obliquely through the 
forearm and is inserted into the bases of the second and third metacarpal 
bones. Its tendon is rendered prominent just proximal to the wrist, 
when the joint is actively flexed ; it lies about half an inch to the lateral 
side of the middle line. This muscle bears the same relation to radial 
deviation of the hand as the flexor carpi ulnaris bears to ulnar deviation 

(p. 145)- f L . 

The Palmaris Longus is absent in about 10 per cent, of subjects. It 
is inserted into the palmar aponeurosis, and its tendon can be distinguished 
to the medial side of the flexor carpi radialis tendon, when the wrist-joint 
is actively flexed. 

The Flexor Digitorum Stiblimis is partly overlapped by the three 
preceding muscles. It breaks up into four tendons, which are inserted 
into the second phalanges of the medial four digits. When the fist is 
tightly clenched, with the wrist extended, a slight hollow appears on 
the medial side of the palmaris longus tendon, and in the floor of this 
depression the tendons for the ring and little fingers can be felt. 

The median nerve passes distally through the forearm, 
deep to the superficial group of muscles. Just distal to the 
elbow-joint, it gives off the volar interosseous nerve, which 
descends on the interosseous membrane and supplies the 
deep muscles of the front of the forearm, namely, the flexor 
pollicis longus, the pronator quadratus and the radial half of 
the flexor digitorum profundus. 

The Flexor Pollicis Longus arises from the anterior aspect of the 
radius and is inserted into the distal phalanx of the thumb. Its tendon 
is overlapped by the tendon of the flexor carpi radialis and is consequently 
difficult to feel', but, if the fist is tightly clenched, a visible depression 
appears on the radial side of the flexor carpi radialis tendon when the 
flexor pollicis longus is contracted. 

The Pronator Quadratics arises from the distal part of the volar surface 
of the ulna and is inserted into a corresponding area on the radius. It 
is very deeply placed and its contractions cannot be appreciated either by 
inspection or by palpation. 



THE BRACHIAL PLEXUS 151 

The Flexor Digitorum Profundus arises from the volar aspects of the 
ulna and interosseous membrane. Near the wrist it breaks up into four 
tendons which are inserted into the distal phalanges of the medial four 
fingers. That part of the muscle which is destined for the ring and little 
fingers is supplied by the ulnar nerve, while the remainder is supplied by 
the volar interosseous. 

In the distal part of the forearm, the median nerve gives off 
a volar cutaneous branch, which supplies the skin over the 
central part of the palm of the hand. Near the wrist, the 
nerve becomes more superficial and lies behind the palmaris 
longus tendon. Neuromata or neuro-fibromata are frequently 
found on the median nerve in this part of its course. 

As it enters the palm of the hand, the median nerve 
divides into a lateral and a medial division. The former 
supplies the skin on the volar aspect of the thumb and the 
radial half of the volar aspect of the index finger, by means 
of digital branches. These nerves are not restricted to the 
volar aspects of the index finger and thumb, and they also 
supply the distal halves of the dorsal aspects of both. 

In addition to its digital branches, the lateral division of 
the median nerve gives off branches to supply the muscles of 
the thenar eminence, which is formed by the abductor pollicis 
brevis, the opponens pollicis and the flexor pollicis brevis. 

The Abductor Pollicis Brevis forms the lateral part of the thenar eminence. 
It arises from the carpus and is inserted into the radial side of the base of 
the proximal phalanx of the thumb. In cases where injury of the median 
nerve near the wrist is suspected, the action of this muscle must be care- 
fully tested. Abduction of the thumb carries it forwards from the palm in 
an antero-posterior plane (p. 147), and it must be distinguished from 
extension, which carries the thumb away from the hand in a lateral 
direction. Pure abduction of the thumb is impossible when the abductor 
pollicis brevis is paralysed, because the abductor longus (extensor ossis 
metacarpi pollicis) is really an extensor muscle. 

The Flexor Pollicis Brevis forms the medial part of the thenar eminence, 
while the Opponens Pollicis lies under cover of both the flexor and the 
abductor. The latter muscle arises from the radial side of the volar aspect 
of the carpus and is inserted into the radial border of the first metacarpal 
bone. When it contracts, it produces a slight amount of medial rotation 



152 THE NERVOUS SYSTEM 

of the first metacarpal at the carpometacarpal joint, and this rotation, com- 
bined with flexion, enables the thumb to be opposed to the little finger. 

The muscles of the thenar eminence are usually the first to 
be involved in progressive muscular atrophy, and they are 
affected with great constancy in those cases of cervical rib 
which give rise to symptoms (see also p. 156): 

The digital nerve to the radial side of the index finger gives 
a branch of supply to the first lumbrical muscle (p. 145). 

The medial division of the median nerve breaks up into two 
branches, which pass to the clefts between the index and middle, 
and middle and ring fingers, respectively. The former supplies 
the second lumbrical muscle. At the cleft, each breaks up 
into digital nerves for the volar aspects of the adjacent 
borders of the two fingers. These digital nerves also supply 
the distal part of the dorsal surface of the fingers (cf. Ulnar 
Nerve, p. 145). 

Injuries of the median nerve may be divided into two 
groups : — (a) Those occurring distal to the origin of the 
motor branches to the flexor muscles of the forearm but 
proximal to the origin of the motor branches to the muscles of 
the thenar eminence. (/>) Those occurring proximal to the 
origin of the motor branches to the flexor muscles of the 
forearm. 

(a) When the median nerve is divided near the wrist, the 
motor symptoms are not very striking. True abduction and 
true opposition of the thumb are impossible, but these move- 
ments are simulated by the abductor pollicis longus (extensor 
ossis metacarpi pollicis) and the extensors, and the flexor 
pollicis longus, respectively. Examination reveals the fact 
that the abduction obtained does not take place in an antero- 
posterior plane (p. 151), while in the simulated opposition the 
metacarpal bone of the thumb is not rotated. 

The paralysis of the first and second lumbricals upsets the 
muscular balance of the hand, and the grasping power is much 
less than might have been expected. The index and middle 
fingers tend to be extended at the metacarpophalangeal and 






THE BRACHIAL PLEXUS 



'53 



flexed at the interphalangeal joints, when the hand is at rest, 
but these fingers retain all their normal movements. 

The sensory symptoms are due to the paralysis of the volar 




A H 

Fio. 67. — The Nerve-supply of the Skin on the Dorsal Aspect 
of the Upper Limb. 

A. The segmental supply. 

/.'. The individual nerves of supply. 



1. Posterior supra-clavicular nerves. 

2. Lateral cutaneous nerve of arm. 

3, 4. Dorsal cutaneous nerve of forearm 
(upper and lower external cutane- 
ous branches of musculo-spiral 
nerve). 

5. Lateral cutaneous nerve of forearm. 

6. Superficial division of radial nerve. 



Dorsal cutaneous branch of ulnar 
nerve. 

Medial cutaneous nerve of forearm 
(internal cutaneous nerve). 

Intercosto-brachial nerve. 

Posterior cutaneous nerve of arm (in- 
ternal cutaneous branch of musculo- 
spiral nerve). 



cutaneous branch and the digital nerves, and, unless tendons 
have been divided in addition, deep sensibility is not inter- 
fered with. As usual in these cases, the area of epicritic loss 



154 THE NERVOUS SYSTEM 

exceeds the area of protopathic loss. It affects the radial 
part of the palm, the volar aspects of the thumb, index, middle 
and ulnar half of the ring finger, and the dorsal aspects of 
the distal halves of the index, middle and ulnar half of the 
ring finger. The dorsum of the thumb is never affected in 
injuries to the median nerve. 

(/;) When the median nerve is divided in the axilla or arm, 
all the flexor and pronator muscles are paralysed, except the 
flexor carpi ulnaris and the ulnar half of the flexor digitorum 
profundus. The ring and the little fingers retain their 
lumbricals and interossei, in addition to their profundus 
tendons, and they are therefore little affected. The middle 
and index fingers, however, only retain their interossei, as both 
the flexor digitorum sublimis and profundus and the first two 
lumbricals are paralysed. They are extended or hyper- 
extended at the metacarpophalangeal joints and extended at 
the interphalangeal joints. Active flexion of these fingers 
can only be carried out at the metacarpophalangeal joints, 
and it is then produced by the interossei. 

The thumb is maintained extended and adducted. Flexion 
of the terminal phalanx is impossible and flexion of the 
proximal phalanx is a weak movement, produced by the un- 
paralysed adductor pollicis. Abduction can be simulated by 
the abductor pollicis longus, as has been described above, 
but, owing to the paralysis of the flexor pollicis longus, 
opposition of any kind, either true or false, is impossible. 

The forearm is held in the supine position and, as both the 
pronator teres and quadratus are paralysed, true pronation is 
impossible. The brachio-radialis is able to initiate the move- 
ment (p. 140), and, if the arm is then abducted to a right 
angle, the weight of the partially pronated hand can complete 
the movement. 

The sensory phenomena are restricted to the same areas as 
before {vide supra), but deep sensibility is absent over the middle 
and index fingers, and, in many cases, over a wider area, which 
is more or less co-extensive with the area of protopathic loss, 



THE BRACHIAL PLEXUS 155 

Segmental Supply of the Muscles of the Upper Limb 

Most of the muscles of the upper limb are innervated by 
more than one segment of the spinal medulla, but the 
clinical evidence (Kocher, Thorburn, Sherren and others) 
appears to show that each muscle is dependent on a single 
segment for its principal action. Thus, the deltoid receives 
branches from both the fifth and sixth cervical nerves, but 
it is completely paralysed when the anterior ramus of the 
fifth is divided. The functions of the additional supply may 
be sensory or they may be motor, subsidiarily to the main 
segment, for muscles contract not only when their particular 
action is desired but also in association with other muscles. 
For example, when a heavy weight is being carried in the 
hand, with the arm by the side, the flexors of the fingers 
apparently do most of the work, but in order to take the 
strain off the ligaments of the wrist, elbow and shoulder- 
joints, the flexors and extensors of the wrist and elbow, the 
deltoid, coraco-brachialis, etc., are all firmly contracted. 

The clinical evidence, unfortunately, is not entirely satis- 
factory, as witnessed by the fact that the leading authorities 
do not always agree with one another with reference to the 
main segments for certain muscles. It seems probable that 
a group of muscles, possessing a common action {e.g. flexors 
carpi radialis and ulnaris, digitorum sublimis and profundus, 
pollicis longus and palmaris longus all assist in flexion of 
the wrist-joint), should receive its nerve-supply from a single 
segment. The segmental supply as put forward by Sherren 
supports this view. Kocher, on the other hand, has come 
to the conclusion that the segmental supply of a muscle 
depends rather on the particular joint on which its principal 
action depends. 

In the present state of existing knowledge, it will perhaps 
be useful to summarise the different views. 

Fifth Cervical Segment. — According to Kocher, this segment 
is responsible for the supply of (1) the abductors and lateral 



156 THE NERVOUS SYSTEM 

rotators of the shoulder, (2) the flexors and supinators of the 
forearm, and (3) the rhomboids. Sherren's views are sub- 
stantially in agreement with Kocher's, but Thorburn refers 
the supra- and the infra-spinatus to the sixth segment. 

Sixth Cervical Segment. — To this segment Kocher and 
Thorburn refer the supply of the muscles which oppose 
those innervated by the fifth, i.e. (1) the adductors and 
medial rotators of the shoulder, (2) the extensors and pronators 
of the forearm, and (3) the serratus anterior. Sherren believes 
that the sixth segment is not so definitely associated with 
particular muscle-groups, and he only includes in its supply 
(1) the clavicular part of the pectoralis major, (2) the pronators, 
(3) the radial extensors of the wrist, and (4) the serratus 
anterior. 

Seventh Cervical Segment. — Kocher includes both the 
flexor and the extensor muscles of the wrist, but Thorburn 
only assigns the flexors to this segment. Sherren only agrees 
with Kocher with reference to the extensor carpi ulnaris 
and he includes the triceps, the extensor muscles of the 
fingers and the sterno-costal portion of the pectoralis major. 
There is, therefore, very little agreement with regard to the 
individual muscles supplied by the seventh cervical nerve, 
probably because it is practically never injured alone, since 
it is the middle, and longest, of the five main nerves which 
constitute the brachial plexus. 

Eighth Cervical Segment. — The flexor and extensor muscles 
of the fingers are innervated by the eighth cervical segment, 
according to Kocher, but Sherren includes the flexors only, 
and, with them, the flexors of the wrist. Thorburn sub- 
stantially agrees with the latter. 

First Thoracic Segment. — According to practically all the 
authorities, this segment is responsible for the supply of the 
small muscles of the hand. In view of the comparative 
unanimity with regard to the fifth cervical segment, it is not 
surprising to find the same agreement with regard to the 
first thoracic, because, on account of their shortness, the 



THE BRACHIAL PLEXUS 157 

anterior rami of C. 5 and T. 1 are subjected to stretching 
much more frequently than the other nerves of the plexus. 

From this summary it may be concluded that existing 
knowledge of the segmental supply of the upper limb is 
definite with reference to the fifth cervical and first thoracic 
segments, but that more data or new methods of examination 
are required before the muscles associated with the inter- 
mediate segments can be definitely determined. 

It will be observed, however, that the muscles of the 
shoulder-girdle and arm are supplied by the upper nerves 
of the plexus, which take origin from the upper part of 
the cervical enlargement of the spinal medulla (p. 40), whereas 
the muscles of the distal part of the limb are supplied by 
the lower nerves. When acute anterior polio-myelitis affects 
the cervical enlargement, it is commonly limited to its upper 
or lower part, and the resulting paralysis is correspondingly 
of the upper arm or lower arm type. 

Segmental Sensory Supply of the Upper Limp 

Just as certain segments of the spinal medulla are associated 
with certain muscle groups, so each segment of the spinal 
medulla is associated with a certain area of skin, and this 
fact is best appreciated when the mode of development of 
the limbs is called to mind. 

The limbs arise as lateral buds from the body of the 
embryo. The upper limb grows out in the lower cervical 
region at right angles to the long axis of the body, and it 
contains prolongations of the lower four cervical and the first 
thoracic segments. It possesses ventral and dorsal surfaces, 
which are separated by cephalic, or pre-axial, and caudal, or 
post-axial borders. The anterior rami of the lower four 
cervical and first thoracic nerves grow out into the bud. The 
fifth cervical nerve is associated with the pre-axial border, 
and the first thoracic with the post-axial border, while the 
intermediate nerves occupy intermediate positions. As the 



158 THE NERVOUS SYSTEM 

limb increases in size, the sixth and seventh cervical nerves 
reach the pre-axial border and the eighth reaches the post- 
axial border (Fig. 68). 

This arrangement is maintained throughout development. 
In Fig. 67 the segmental distribution of the cutaneous nerves 
of the upper limb is represented diagram mat ically. The fifth 
and sixth cervical nerves supply the lateral aspect of the arm 
and forearm ; while the seventh does not appear on the 
volar aspect till the hand is reached. The medial aspect 
of the limb is supplied by the eighth cervical and the first 
and second thoracic nerves. On the dorsal aspect of the 



/ c4 


1 C ^-— 


. S C A 


J C5 


-^ C 5 


f C 6 


C 6 


( C? 


V C 5 


C5 


N=« 


"" T 1 




~X n 



Stage I. Stage II. 

Fig. 68. — Diagram representing the development of the Upper Limb, and 
the segmental arrangement of its Sensory Nerve-supply. 

limb, the arrangement is precisely similar except that the 
seventh cervical nerve reaches the skin of the forearm. This 
description is in harmony with the views of Edinger, Purves- 
Stewart and others, but it is not accepted by Sherren, who 
holds that the whole of the lateral aspect of the limb is 
supplied by the fifth, sixth and seventh cervical nerves and 
that the areas supplied by each are practically co-extensive. 

Lesions of the Brachial Plexus 

In accordance with the segmental motor and sensory supply 
of the upper limb, it is possible to determine the exact site 
of injuries of the spinal medulla or of the anterior rami of 
the spinal nerves. in the lower cervical region. Injuries of 



THE^BRACHIAL PLEXUS 159 

the plexus, however, may involve the trunks or cords, and 
certain facts must be borne in mind when the site of any 
such lesion is being determined. 

When the fifth cervical segment is involved, the actions of the 
rhomboids and the supra- and infra-spinati must be carefully 
investigated. If the rhomboids are found to be paralysed, 
then the nerve must be affected close to the intervertebral 
foramen. If the rhomboids are not involved and the supra- 
and infra-spinati are paralysed, then the lesion must have caught 
the nerve just prior to the formation of the upper trunk of the 
plexus, but if both groups have escaped, the lesion is one of 
the upper trunk. Unfortunately, it is not easy to ascertain 
whether these groups are paralysed or have escaped. In the 
case of the rhomboids, the position of the scapula is altered 
somewhat on the affected side. It occupies a slightly lower 
position and, the bone being rotated clockwise (as viewed from 
in front) by the serratus anterior, the inferior angle is farther from 
the median plane than it is on the sound side. The examination 
of the supra-spinatus is rendered difficult because the muscle is 
almost entirely covered by the trapezius and is nowhere sub- 
cutaneous. Fortunately, sufficient of the infra-spinatus is 
exposed to enable its electrical reactions to be examined. 

When the sixth segment is involved, the action of the serratus 
anterior must be tested. Forward pushing movements against 
resistance make the digitations of origin stand out prominently 
on the lateral thoracic wall, in moderately well-developed 
subjects. Ability to flex the shoulder beyond an angle of 
yo° indicates that the serratus anterior is acting normally. If 
the serratus anterior is paralysed (p. 132), the sixth cervical nerve 
is involved close to its exit from the intervertebral foramen. 

When the first thoracic segment is involved, the condition 
of the cervical sympathetic gives a clue to the situation of 
the lesion. When it is affected, the lesion must be situated 
between the point where the first thoracic nerve gives off its 
white ramus communicans and the point at which it leaves 
the vertebral canal. 



160 THE NERVOUS SYSTEM 

THE INTERCOSTAL NERVES 

The Anterior Rami of the upper eleven Thoracic Nerves 
form the intercostal nerves ; but the first intercostal is very 
small and only supplies the first intercostal muscles. The 
second, third, fourth, fifth and sixth not only supply the 
intercostals but also give off lateral and anterior cutaneous 
branches. The lateral cutaneous nerves pierce the deep fascia 
near the mid-axillary line, and divide into anterior and 
posterior branches, which supply the skin over the lateral 
aspect of the body (Fig. 69). The lateral branch of the second 
intercostal nerve, however, supplies the skin on the postero- 
medial aspect of the arm and is termed the intercosto-brachial 
nerve. Near the sternum, the intercostal nerves turn forwards 
and their terminal branches constitute the anterior cutaneous 
nerves. 

In consequence of the areas supplied by the second inter- 
costal nerve, it is not surprising to find that, in the condition 
of " thoracic-ulnar analgesia," which is frequently an early sign 
of tabes dorsalis, there is loss of sensibility over the upper 
part of the chest and the medial side of the arm. 

It must be remembered that although the intercostal nerves 
follow a very oblique course as they pass round the body, 
their branches descend all to the same level before supplying the 
skin. Each intercostal nerve is responsible for the supply of a 
horizontal band of skin, which corresponds in level to the 
terminal twigs of its cutaneous branches. 

The lower five intercostal nerves and the subcostal nerve 
correspond to the upper intercostal nerves, except that their 
terminal branches extend beyond the costal margin and gain 
the anterior abdominal wall. On this account, the anterior 
abdominal wall is often the site of referred pain in cases of 
pneumonia and pleurisy. These nerves give off lateral and 
anterior cutaneous branches, but, in addition to supplying the 
intercostal muscles, they innervate the rectus abdominis, the 
internal and external obliques and the transversus muscle. 



THE INTERCOSTAL NERVES 161 

The Rectus Abdominis is a strap-like muscle, which arises 
from the front of the pubis and extends upwards to the xiphoid 
process and the adjoining costal cartilages. When it contracts, 
it helps to flex the vertebral column, but, like the lateral 




{Photo !iy Alinari. 
Fig. 69. — The Nerve-supply of the Anterior Aspect of the Trunk. 

muscles of the abdominal wall, its main action is to assist 
expiration by compressing the abdominal viscera so that the 
liver may elevate the relaxed diaphragm. Further, in common 
with the lateral muscles, the rectus normally influences the 
muscular tonus of the alimentary canal, and improvement of 
11 



i6 2 THE NERVOUS SYSTEM 

the tonus of these muscles is an important step in the treat- 
ment of constipation. 

The External Oblique, the Internal Oblique and the Trans- 
versus are flat, fleshy muscles, which form the lateral portions of 
the muscular abdominal wall. Anteriorly, where they are related 
to the rectus, they form thin aponeurotic sheets, which blend 
with one another and with those of the opposite side in the 
linea alba. Their functions are the same as those of the rectus, 
but, whereas the rectus helps to flex the vertebral column in an 
anteroposterior plane, the obliques help to produce lateral 
flexion of the vertebral column. 

It is important to recognise that the muscles of the anterior 
and lateral abdominal walls are segmental in origin, i.e. the 
external oblique corresponds to a number of external intercostal 
muscles fused together into one sheet. These muscles are all 
supplied by the lower six thoracic and the first lumbar nerves, 
and each nerve supplies a particular segment. As a result, 
the muscles are able to contract in segments, and, although 
this contraction cannot be effected voluntarily, it can be 
produced reflexly. A localised area of contraction indicates 
that a " focus of irritation " is present in the particular segment 
of the spinal medulla which innervates the muscular segment in- 
volved, and this focus may be due to irritation of the peripheral 
sympathetic fibres which are associated with that segment. 
For example, the upper half of the right rectus is innervated 
by the seventh, eighth and ninth thoracic nerves, and these 
segments of the spinal medulla not only innervate the muscle 
but also receive afferent impulses via the sympathetic from the 
gall-bladder and bile-ducts (p. 264). As a result, cholecystitis 
is frequently associated with a localised contraction of the 
upper part of the right rectus muscle. 

Similar contracted areas are often found in gastric ulcer 
(p. 250), appendicitis (p. 279), renal colic (p. 364) and other 
abdominal conditions. 

In herpes zoster, the eruption is found to be limited to the 
area of sensory supply of a given thoracic nerve, and it therefore 



THE LUMBAR PLEXUS 163 

forms a horizontal strip round the body. In the girdle pains 
of tabes dorsalis, the pain is experienced in the same hori- 
zontal strips, but it is not uncommon for several adjoining 
areas to be affected at the same time. 

Areas of hyperesthesia are frequently found in the skin of 
the abdominal wall, and, like the areas of localised muscular 
contraction, they are due to the presence of a " focus of 
irritation" (p. 195) in the' spinal medulla. The level at which 
they occur may be of help in determining the diagnosis. It 
is useful, for this purpose, to remember that the umbilicus lies 
in the zone supplied by the tenth thoracic nerve, and that the 
first lumbar nerve is restricted to a very small area in the lowest 
part of the abdominal wall. 

THE LUMBAR PLEXUS 

The Anterior Rami of the upper four Lumbar Nerves take 
part in the formation of the Lumbar Plexus. After leaving 
the vertebral canal, they enter the substance of the psoas 
major muscle, where the plexus is formed. Cases of psoas 
abscess in which the muscle is infiltrated by pus may be ac- 
companied by muscular paralysis or by pain which is referred 
to the peripheral distribution of the sensory branches of the 
plexus. 

The Ilio-hypogastric and the Ilioinguinal Nerves arise 
from the first lumbar nerve, very often by a common trunk. 
They appear at the lateral border of the psoas major and run 
laterally, at first posterior to the kidney. In this part of their 
course they may be compressed by tumours of the kidney, and 
the pain is referred to their distribution. 

The ilio-hypogastric nerve gives off an iliac branch, which 
crosses the iliac crest to supply the skin over the lateral part of 
the buttock, and it then runs forwards, terminating by supply- 
ing the skin over the lower part of the rectus muscle (Fig. 69). 
In addition to its sensory branches, the nerve usually helps 
to supply the lateral muscles of the abdominal wall. 



164 



THE NERVOUS SYSTEM 



The ilioinguinal nerve emerges through the subcutaneous 
, 1 H u Bxn 




rfrjv' 1 ■ miss; 







FlG. 70. — The Lumbar, Sacral and Pudendal Plexuses. The abdominal 
and pelvic portions of the sympathetic trunks are also shown. 
(Turner's Anatomy.) 

7. Sciatic nerve. 

S. L. V joining part of L. IV to form the 

lumbo-sacral cord. 
a. Sympathetic trunk. 



1. Ilio-hypogastnc nerve. 

2. Ilio-inguinal nerve. 

3. Lateral cutaneous nerve of thigh. 

4. Genito-femoral nerve. 

5. Femoral (anterior crural) nerve. 

6. Obturator nerve. 



/». Coeliac (semilunar) ganglion. 
c. Ganglion impar. 



inguinal ring (external abdominal ring) and supplies the 
adjoining area of skin over a limited extent. It may be 






THE LUMBAR PLEXUS 165 

compressed against the superior crus (pillar) of the ring by 
large inguinal hernias and give rise to painful symptoms. 

The Genito-femoral Nerve arises from the first and second 
lumbar nerves, and descends on the surface of the psoas major. 
It divides into the lumbo-inguinal {femoral branch) and the 
external spermatic nerves (genital branch). The former varies 
considerably in size. Usually, it supplies a small area of 
skin just distal to the middle of the inguinal ligament (of 
Poupart), but occasionally it extends as far as the knee, 
supplying a large area of skin on the front of the thigh. 

The external spermatic nerve enters the spermatic cord 
and supplies the cremaster muscle, which constitutes one of 
the coverings of the cord and testis. In addition, it supplies 
a sensory branch to the tunica vaginalis testis (p. 375) 
(Mackenzie). 

The Cremaster Muscle is derived from the lower border 
of the internal oblique and it consists of a number of muscular 
loops, of varying size, which pass downwards on the spermatic 
cord and then ascend to the inguinal ligament (of Poupart). 
When the muscle contracts, it drags the testis upwards 
towards the subcutaneous inguinal ring. 

The cremasteric reflex depends on the integrity of the 
genito-femoral nerve and the segments of the spinal medulla 
from which it arises. When the skin of the proximal part 
of the front of the thigh is lightly stroked, the testis is drawn 
upwards in the scrotum. This reflex is particularly active in 
children, but it is not so easy to elicit in the adult. The 
afferent impulse passes along the lumbo-inguinal nerve and 
reaches the second lumbar segment of the spinal medulla. 
From there, the efferent impulse is conveyed to the cremaster 
muscle by the external spermatic nerve. The cremasteric 
reflex is increased in lesions of the spinal medulla above the 
second lumbar segment. 

The Lateral Cutaneous Nerve of the Thigh arises from the 
second and third lumbar nerves. After emerging from the 
psoas major, it crosses the iliacus and reaches the lateral 



1 66 THE NERVOUS SYSTEM 

extremity of the inguinal ligament, behind which it passes 
to enter the thigh. As it lies on the iliacus, it is placed 
behind the caecum, on the right side, and the iliac colon, on 
the left side of the body. It supplies the skin of the lateral 
aspect of the thigh and extends as far as the knee-joint. In 
addition, it gives off branches, which pass backwards to the 
buttock and back of the thigh. 

The Femoral Nerve (Anterior Crural) (L. 2.3.4.) is the 
biggest and most important branch of the lumbar plexus. 
It enters the thigh behind the inguinal ligament, in the groove 
between the psoas major and the iliacus, but it supplies the 
latter muscle before it leaves the pelvis. 

In the thigh, it gives off — (a) Motor branches, which supply 
the quadriceps femoris, the sartorius and the pectineus ; 
(b) articular branches to the hip- and knee-joints ; and (c) the 
media/ and intermediate cutaneous nerves of the thigh and the 
saphenous nerve. 

The Quadriceps Femoris comprises the Rectus Femoris, the Vastus 
Medialis, Vastus Intermedius (Crureus) and the Vastus Lateralis. 

The Rectus Femoris arises from the antero-inferior spine of the ilium 
and is inserted into the proximal border of the patella. It acts as a flexor 
of the hip and as an extensor of the knee. Consequently, it forms a 
prominent elevation on the front of the thigh, when the hip-joint is 
flexed and the knee-joint extended, the limb not being supported. 

The three Vasti muscles arise from the femur and are inserted into the 
patella. The Medialis and Lateralis form distinct prominences at the 
sides of the knee, when they are called on to keep the leg extended 
against gravity ; the elevation produced by the medialis extends more 
distally than that produced by the lateralis. 

The Sartorius arises from the antero-superior spine of the ilium and 
passes distally and medially to reach the medial side of the thigh. It 
then descends vertically across the medial aspect of the knee-joint and 
is inserted into the proximal part of the antero-medial surface of the tibia. 
It acts as a flexor of both the hip- and the knee-joints, and it can be made 
to stand out when the lower limb, flexed at both joints, is elevated from 
the ground. Since the sartorius is supplied by the femoral nerve, its 
action as a flexor of the knee is of special interest (p. 175). 

The Pectineus lies in the proximo-medial part of the thigh. It arises 
from the superior ramus of the pubis and is inserted into the posterior 



THE LUMBAR PLEXUS 167 

surface of the proximal part of the femoral shaft. As it passes from its 
origin to its insertion, it crosses the anterior aspect of the capsule of the 
hip-joint, and it therefore acts as a flexor of that joint. In addition, 
it is a weak adductor. 

The Intermediate Cutaneous Nerve of the thigh supplies 
the skin on the anterior aspect of the thigh and takes part 
in the formation of the prepatellar plexus. Its area of 
distribution is overlapped by the medial and the lateral 
cutaneous nerves and also by the lumbo-inguinal nerve (p. 165). 

The Medial Cutaneous Nerve of the thigh is distributed 
to the skin over the medial aspect of the thigh and knee. 
Its branches overlap not only the branches of the intermediate 
cutaneous but also the branches of the posterior cutaneous 
(small sciatic) nerve. 

The Saphenous Nerve accompanies the femoral artery in 
the proximal two-thirds of the thigh. It pierces the deep 
fascia opposite the adductor tubercle and descends along the 
medial aspect of the leg. Finally it terminates about the 
middle of the medial border of the foot. 

Paralysis of the Femoral Nerve is a very uncommon 
condition. When the psoas major and the iliacus are involved 
in addition to the quadriceps, the sartorius and the pectineus, 
the movements of flexion at the hip and extension at the 
knee are greatly weakened, but they are not impossible. 
When the thigh is hyperextended and rotated laterally, the 
adductors (obturator nerve) and the tensor fascice latas 
(superior gluteal nerve, p. 172) can produce flexion of the hip 
and the latter muscle alone is able to extend the knee-joint. 
On this account, the patient may be able to walk with the help 
of a stick. 

When the femoral nerve is completely divided, sensory 
disturbances occur in the distal part of the antero-medial 
aspect of the thigh, and in the medial aspect of the leg and 
ankle, in the area supplied by the saphenous nerve. It is 
in the latter area that the greatest alterations in sensibility 
occur, but deep sensibility is not affected. 



1 68 



THE NERVOUS SYSTEM 






The Obturator Nerve also arises from the second, third and 
fourth lumbar segments, but it pursues a different course 
from that adopted by the femoral nerve. It pierces the medial 










Fig. 71. — The Nerve-supply of the Skin on the Anterior Aspect 
of the Lower Limb. 

A. The individual nerves of supply. 

B. The segmental supply. 



1. Lateral cutaneous nerve. 

2. Lumbo-inguinal nerve (crural branch 

of genito-crural nerve). 

3. Intermediate (middle) and medial 

cutaneous nerves. 

4. Obturator nerve. 



5. Lateral sural nerve. 

6. Saphenous nerve. 

7. Superficial peroneal (musculocutan- 

eous) nerve. 

8. Medial branch of deep "peroneal (ant- 

erior tibial) nerve. 



border of the psoas major and passes forwards on the lateral wall 
of the pelvis, just below the brim, lying in the floor of the 
fossa ovarica in the female (p. 393). It leaves the pelvis by 



THE LUMBAR PLEXUS 169 

passing through the uppermost part of the obturator foramen, 
and in this way it gains the medial compartment of the thigh. 
The branches of the obturator nerve are distributed (1) to 
the obturator externus and to the adductor group of muscles ; 
(2) to the hip- and knee-joints; and (3) to the skin over the 
medial aspect of the thigh. 

The Obturator Externus arises from the outer surface of the obturator 
membrane and, passing first below and then behind the capsule of the hip- 
joint, is inserted into the trochanteric fossa. It is a powerful lateral rotator 
of the thigh, but its paralysis cannot be satisfactorily demonstrated, because 
( 1 ) the muscle is so deeply placed that the examination of its contractility 
or its electrical reactions is practically impossible, and (2) the thigh is 
furnished with several lateral rotator muscles, e.g. obturator internus, 
quadratus femoris, etc., which are supplied by the sacral plexus. 

The Adductor Group consists of the Adductors Longus, Brevis and 
Magnus and the Gracilis. 

The Adductors Longus and Brevis extend from the pubis to the dorsal 
aspect of the shaft of the femur. They are powerful adductors and they 
assist in flexing the hyperextended thigh. 

The Adductor Magnus arises from the pubis and its origin extends back- 
wards on to the ischial tuberosity. It is inserted into the whole length of 
the dorsal aspect of the femur, and, distally, it reaches the adductor tubercle 
on the medial condyle. The fibres which arise from the pubis are attached 
to the proximal part of the femur, whereas those which arise from the 
ischial tuberosity run almost vertically to gain the adductor tubercle. On 
account of the arrangement of its fibres, the action of the adductor magnus 
is slightly complicated. 

Acting as a whole, the muscle is a powerful adductor. The upper 
fibres help to flex the hyperextended thigh, but the lower fibres help to 
extend the flexed thigh. In consequence of the latter action, the 
adductor magnus receives an additional nerve of supply, from the sciatic 
nerve. 

The Gracilis arises from the pubis and passes distally along the medial 
aspect of the thigh to be inserted into the proximal part of the antero- 
medial surface of the tibia. It is a weak adductor and flexor of the hip, 
but it assists in flexion and medial rotation of the knee (p. 175). 

The Articular Branches help to supply the synovial mem- 
brane of the hip- and knee-joints, but the genicular branch is 
by no means constant. It appears likely that pain referred 
from the hip-joint to the region of the knee has no connexion 



170 THE NERVOUS SYSTEM 

with the genicular branch of the obturator nerve. The 
articular branches of the femoral nerve are stimulated on the 
hip-joint and an "overflow" (p. igi) occurs in the spinal 
medulla in such a way as to stimulate the cells which receive 
afferent impulses from the medial and intermediate cutaneous 
nerves of the thigh. In this way the pain is referred to the 
region of the knee. 

The Cutaneous Branches of the obturator nerve supply a 
small area on the medial aspect of the thigh which is over- 
lapped by the adjoining medial and posterior cutaneous nerves. 

The Obturator Nerve may be injured in the pelvis by 
tumours in connexion with the uterus or rectum, or during the 
passage of the foetal head at parturition. The first sign of 
the involvement of the obturator nerve in these cases is pain 
which is referred to the medial aspect of the thigh. 

When the obturator nerve is completely divided, there is no 
alteration discoverable in the sensibility of the skin of the 
thigh, but there is complete paralysis of the adductor muscles, 
a condition which is best appreciated when the patient is 
examined lying flat on his back with the lower limbs extended. 
In this position, the affected limb is maintained in a position 
of slight abduction by the unopposed abductor muscles. On 
the other hand, when the patient assumes the erect attitude, 
the noticeable deformity may be very slight, as the abductor 
muscles are then opposed by the weight of the limb. 

THE SACRAL PLEXUS 

The Sacral Plexus is formed by a part of the fourth and 
the whole of the fifth lumbar, the first, second and part of the 
third sacral nerves. The lumbo-sacral cord, which is formed 
by the union of the fifth lumbar with a branch of the fourth 
lumbar nerve, unites with the first and second and a branch of 
the third sacral nerve. In this way a large band is constituted, 
which, although mainly continued as the Sciatic A r erve, gives 
off several smaller branches, 



THE SACRAL PLEXUS 



171 



On the left side, the plexus is situated posterior to the rectum, 
and this constitutes an important relationship, for the rectum 
(p. 283) is capable of enormous distension, so that it may com- 



Dxn 




Fig. 72. — The Lumbar, Sacral and Pudendal Plexuses. The abdominal 
and pelvic portions of the sympathetic trunks are also shown. 
(Turner's Anatomy.) 

7. Sciatic nerve. 8. L. V joining part of L. IV to form the lumbo-sacral cord. 

press not only the left but also the right sacral plexus. As a 
result, the patient may have all the symptoms of sciatica, and 
it is of great benefit to make the thorough evacuation of the 



172 



THE NERVOUS SYSTEM 



rectum a routine measure in the initial stages of treatment of 
all cases of sciatica. 

Owing to its position, the plexus may be injured during 
parturition in difficult labours. 

The Superior Gluteal Nerve (L. 4 and .5, and S. 1) arises 
from the posterior aspect of the plexus and enters the gluteal 
region by passing through the great sciatic foramen. It gives 
off no cutaneous branches, but it supplies the glutaei, medius 
and minimus, and the tensor fascise latae. 

The Gluteus Medius arises from the dorsum ilii and its fibres converge 
on the lateral aspect of the greater trochanter of the femur, passing above 
the capsule of the hip-joint, from which they are separated by the gluteus 
minimus. The medius acts as a powerful abductor of the thigh ; in 
addition, the anterior fibres act as flexors and medial rotators, while the 
posterior fibres act as lateral rotators of the hip. The upper and anterior 
part of the muscle is covered by the skin and fascise, but the greater bulk 
of the muscle is hidden from view by the gluteus maximus. 

The Glittans Minimus lies under cover of the preceding muscle and is 
therefore deeply placed. From their origin on the lower part of the 
dorsum of the ilium, the fibres converge on the anterior aspect of the 
greater trochanter where they receive insertion. The action, like the 
nerve-supply, of this muscle is the same as that of the gluteus medius. 

The Tensor Fascia Late arises from the anterior part of the lateral lip 
of the iliac crest and is inserted into a splitting of the deep fascia on the 
lateral aspect of the thigh. Through the ilio-tibial tract (band) of the deep 
fascia, the muscle exercises an extensor action on the knee-joint, and by 
bracing the tract it helps to relieve the strain from the quadriceps when 
the erect attitude is maintained. Further, the tensor fasciae late acts as 
a weak abductor and medial rotator of the hip-joint. 

The llio-tibial Tract (Band) is the thickened lateral part of the deep 
fascia of the thigh. Distally, it blends with the periosteum over the 
lateral condyle of the tibia and the head of the fibula and proximally it is 
attached to the lateral lip of the iliac crest. It forms such a strong sheet 
that extravasations of blood on its deep surface do not rupture through it, 
but extend distally or forwards before discoloration becomes visible. 

The Inferior Gluteal Nerve (L. 5 and S. 1 and 2) also arises 
from the posterior aspect of the plexus and passes through the 
greater sciatic foramen to enter the buttock, where it is 
entirely distributed to the gluteus maximus. The latter muscle 



THE SACRAL PLEXUS 173 

together with the thick layer of superficial fascia which covers 
it, forms the normal prominence of the buttock. It has a wide 
origin from the ilium, sacrum, coccyx and sacro-tuberous (great 
sacro-sciatic) ligament and its fibres run downwards and laterally 
to be inserted into the ilio-tibial tract and the dorsal aspect of the 
proximal part of the femur. The principal action of the muscle 
is to extend the thigh, but it is also a powerful lateral rotator 
and an abductor. When the lower limbs are fixed, the glutasi 
maximi help to extend the trunk on the hip-joints. 

The Qitadratus Femoris is a small muscle, which extends from the lateral 
border of the ischial tuberosity to the posterior aspect of the proximal part 
of the femur. It acts as a lateral rotator of the thigh, and is supplied by 
a special branch from the sacral plexus (L. 4 and 5, and S. 1). The same 
nerve supplies the inferior gemellus. 

The Obturator Inter mis arises from the pelvic surface of the obturator 
membrane and from the adjoining area of bone. Its tendon leaves the 
pelvis by passing through the lesser sciatic foramen. In the buttock, 
the tendon is joined by the two small gemelli muscles, which arise from 
the lesser sciatic notch, and all three have a common insertion into the 
apex of the greater trochanter. When the thigh is flexed, they help the 
movement of abduction, but, when the thigh is extended, they assist in 
lateral rotation. The obturator interims and the superior gemellus are 
both supplied by a special branch from the sacral plexus (L. 5 and S. I 
and 2), while the inferior gemellus receives its supply from the nerve to 
the quadratus femoris. 

The Sciatic Nerve is the largest and most important branch 
of the sacral plexus. It receives fibres from the fourth and 
fifth lumbar nerves and also from the first, second and third 
sacral nerves. Entering the buttock through the greater 
sciatic foramen, the sciatic nerve descends vertically into the 
thigh. In its proximal part it lies under cover of the gluteus 
maximus and, just before it emerges, it is placed mid -way 
between the ischial tuberosity and the greater trochanter. The 
nerve is crossed by the long head of the biceps and, in the 
rest of its course, it is overlapped by the hamstring muscles. 
The projections formed by the ischial tuberosity and the greater 
trochanter of the femur protect the nerve from violence, but it 
may be injured by falls in which the edge of some hard substance 



174 THE NERVOUS SYSTEM 

forces its way between the two bony prominences. In its 
course, the sciatic nerve crosses the posterior (or extensor) 
aspect of the hip-joint, while its terminal branches are related 
to the posterior (or flexor) aspect of the knee-joint. On 
account of these relationships, the sciatic, nerve is put on the 
stretch when the hip-joint is flexed, provided that the knee- 
joint is in the position of extension. In neuritis of the sciatic 
nerve, this movement causes intense pain, which disappears 
on flexion of the knee, on account of the resulting relaxation 
of the terminal branches. 

The Sciatic Nerve terminates about the middle of the thigh 
by dividing into the Tibial (Internal Popliteal) and the Common 
Peroneal (External Popliteal) Nerves, but these two parts, 
although wrapped up in the same fibrous sheath in the sciatic 
nerve, are quite distinct from one another right up to their 
origins from the sacral plexus. In the proximal part of the 
thigh, the nerve supplies branches to the semimembranosus, 
the semitendinosus and the long head of the biceps (through 
its tibial part) and to the short head of the biceps (through 
its peroneal part). The last-named branch may arise in the 
distal part of the thigh from the common peroneal nerve itself. 

The Semimembranosus arises from the ischial tuberosity and passes 
distally along the medial side of the back of the thigh. It forms one of 
the proximo-medial boundaries of the popliteal fossa, and its tendon can be 
readily palpated in that position when the knee is strongly flexed. It is 
inserted into the posterior aspect of the medial condyle of the tibia. 

The Semitendinosus also arises from the ischial tuberosity and passes 
distally on the surface of the preceding muscle. Its tendon can also be 
palpated at the proximo-medial side of the popliteal fossa, and, finally, it 
is inserted into the proximal part of the medial surface of the tibia. 

Both these muscles act as flexors of the knee and as medial rotators of 
the leg on the femur. 

The Biceps has two heads of origin. The long head arises from the 
ischial tuberosity and the short head from the dorsal aspect of the femur. 
The tendon of the biceps forms the proximo-lateral boundary of the 
popliteal fossa and it can he traced distally to its insertion into the head 
of the fibula, when the knee is strongly flexed. It acts as a flexor of the 
knee and as a lateral rotator of the leg on the femur. 






THE SACRAL PLEXUS 175 

In addition to acting on the knee-joint, the three preceding muscles act 
as extensors of the hip-joint, to the posterior aspect of which they are 
related. It is interesting to observe that, while the thigh may be extended 
without flexing the knee, the latter joint cannot be flexed unless the hip- 
joint also is flexed at the same time. 

When the hamstrings are completely paralysed, flexion of 
the knee is still possible but the movement is not a powerful 
one. It is carried out by the sartorius and the gracilis, 
which, unlike the other flexor muscles, depend for their 
nerve-supply on the femoral and the obturator nerves 
respectively. 

The Tibial Nerve (Internal Popliteal) arises from the 
sciatic in the middle of the thigh and descends vertically 
through the popliteal fossa in the middle line of the limb. In 
the distal part of the fossa, it passes under cover of the 
superficial muscles of the calf and runs distally to a point 
mid-way between the medial malleolus and the point of the 
heel, where it divides into the lateral and medial plantar 
nerves. 

In the popliteal fossa, the tibial nerve gives off — (a) Articular 
branches to the knee-joint, (/>) motor branches, and (c) the medial 
sural nerve (ramus communicans tibialis). 

(b) The motor branches are supplied to both heads of the 
gastrocnemius, the plantaris, the popliteus and the soleus. 

The Gastrocnemius arises by two heads, one from the neighbourhood 
of each femoral condyle, and these two fleshy bellies are mainly responsible 
for the formation of the prominence of the calf. About the middle of the 
back of the leg, they are attached to a common tendon, which is joined 
at a more distal level by the tendon of the soleus. In this way the tendo 
calcaneus (Achillis) is formed and it is inserted into the posterior aspect of 
the calcaneus. When the gastrocnemius contracts, it flexes the knee- 
joint and plantar-flexes the ankle. 

The Sotezes, which lies under cover of the gastrocnemius and projects 
beyond its medial border, arises from the posterior aspects of both the tibia 
and the fibula and unites with the tendon of the gastrocnemius. It acts 
solely as a plantar flexor of the foot. 

The Plantaris is a small muscle which arises from the femur, just 
proximal to the lateral condyle, and is inserted into the calcaneus. It has 



176 



THE NERVOUS SYSTEM 



a long thin tendon, which is placed between the gastrocnemius and the 
soleus. Its action is the same as that of the gastrocnemius. 

The Popliteus arises from the lateral aspect of the lateral condyle, within 
the articular capsule of the knee-joint. It crosses the lateral aspect of the 
joint and is inserted into the proximal part of the posterior surface of the 
tibia. When it contracts, the popliteus flexes the knee and rotates the leg 
medially on the femur. This muscle is deeply placed, in the floor of the 
distal part of the popliteal fossa, and its contractions cannot be appreciated 
on the surface of the limb. 

The Medial Sural Nerve descends in the interval between 
the two heads of the gastrocnemius and pierces the deep 
fascia. It unites with the ramus anastomoticus peronaeus 
(nervus communicans fibularis) (p. 178) to form the nervus 
suralis (short saphenous), and this nerve supplies the skin on 
the postero-lateral aspect of the leg, the lateral border of the 
foot and of the little toe. 

As the tibial nerve descends through the posterior com- 
partment of the leg, it gives off no sensory branches but it 
supplies the group of deep muscles, which includes the tibialis 
posterior, the flexor digitorum and hallucis longus. 

The Tibialis Posterior arises from the posterior aspects of both bones of 
the leg and descends behind the medial malleolus. It then passes forwards 
and is inserted mainly into the tuberosity of the navicular bone, but it gives 
off additional slips to all the other tarsal bones except the talus and, also, 
to the middle three metatarsals. When it contracts, the tibialis posterior 
plantar- flexes the foot and, at the same time, it inverts the foot, i.e. lifts 
the medial border of the foot from the ground so that the sole of the foot 
looks medially. But, while these movements are the result of the active 
contraction of the muscle, its normal tonus helps to maintain the arches of 
the foot. 

The Flexor Digitorum Longus and the Flexor Hallucis Longus arise, 
respectively, from the posterior aspects of the tibia and of the fibula. They 
pass behind the medial malleolus and then run forwards in the sole of the 
foot. Their actions on the digits are clearly explained by their names, 
but, in addition, they both assist the movement of plantar flexion at the 
ankle. Further, like the tibialis posterior, they both help to maintain the 
normal arches of the foot. 

The Arches of the Foot. — In order to distribute the weight of the body 
and to give elasticity to the step in walking and running, the bones of the 



THE SACRAL PLEXUS 177 

foot are arranged to form a transverse and an antero-posterior arch. The 
latter is most pronounced along the medial border of the sole and its key- 
stone is formed by the head of the talus (astragalus), which occupies the 
interval between the sustentaculum tali of the calcaneus (os calcis) and the 
tuberosity of the navicular (scaphoid). The sustentaculum tali can be felt 
immediately below the medial malleolus, and the tuberosity of the navicular 
forms a prominent elevation about I \ inches farther forwards on the medial 
border of the foot. The plantar calcaneonavicular ("spring") ligament 
extends between these two bones and supports the head of the talus. 
Although of great strength, it would be unable to support the talus were 
it not in turn supported by the tendons of certain muscles. 

As the tendons of the tibialis posterior, the flexor digitorum longus and 
the flexor hallucis longus proceed to their respective insertions, they are 
closely related to the plantar surface of the plantar calcaneonavicular 
ligament. Further, the tendons of the two latter muscles cross one another 
in the sole of the foot, and the tendinous sling so formed gives additional 
support to the arch of the foot. 

So long as the tonus of these muscles is good, the antero-posterior arch 
of the foot remains intact, but, when the muscles are poorly developed, 
they become fatigued if called upon to lend support for prolonged periods. 
In this event, the muscles lose their tonus and become relaxed. As a 
result, the head of the talus is dependent for its principal support on the 
plantar calcaneonavicular ligament, which soon stretches. The head of 
the talus thus sinks downwards and the antero-posterior arch of the foot 
collapses. 

The transverse arch of the foot is most pronounced opposite the bases of 
the metatarsal bones and it depends for its support principally on the 
peronreus longus (p. 179). 

In the condition of flat-foot, both arches disappear and the elastic spring 
of the step is entirely lost. 

After giving off the Medial Calcanean Nerve, which arises 
near the ankle-joint and supplies a variable area of skin over 
the medial aspect of the heel, the tibial nerve terminates, 
about midway between the medial malleolus and the point of 
the heel, by dividing into the medial and lateral plantar nerves. 

The distribution of the Medial Plantar Nerve in the foot 
corresponds fairly accurately to the distribution of the median 
nerve in the palm of the hand. It supplies four of the small 
muscles of the sole, but its sensory branches are of greater im- 
portance than its motor branches. The cutaneous brandies 
12 



178 THE NERVOUS SYSTEM 

supply the medial half of the sole of the foot and the medial 
three and a half digits (cf. Median Nerve, p. 151). 

The distribution of the Lateral Plantar Nerve in the foot 
corresponds, in a similar manner, to the distribution of the 
ulnar nerve in the palm of the hand. It gives off numerous 
motor branches, and its cutaneous branches supply the lateral 
half of the sole of the foot and the lateral one and a half digits 
(cf. Ulnar Nerve, p. 145). 

There is little of practical importance in connexion with 
the individual muscles of the sole of the foot and, in con- 
sequence, no description of them will be given. 

The Common Peroneal Nerve (External Popliteal) arises 
from the sciatic in the middle of the thigh and runs distally 
and laterally through the popliteal fossa, in close relation to 
the tendon of the biceps. It passes behind the head of the 
fibula and then runs forwards across the lateral aspect of the 
neck of the bone. In both situations it can be palpated, and it 
is therefore exposed to injury from bruising, etc. Just distal to 
the head of the fibula, the common peroneal nerve ends by 
dividing into the superficial (musculocutaneous) and the deep 
peroneal (anterior tibial) nerves. 

In the popliteal fossa, the common peroneal gives off no 
muscular branches, but it gives origin to two cutaneous nerves. 
The lateral sural nerve runs forwards and distally to supply 
the skin on the front of the leg (Fig. 73) ; the ramus anastom- 
oticus peronseus (ramus communicans fibularis) passes dis- 
tally over the lateral head of the gastrocnemius, and unites 
with the medial sural nerve to form the nervus suralis (p. 176). 

The Superficial Peroneal (Musculo - cutaneous) Nerve 
enters the lateral compartment of the leg and supplies the 
peronsus longus and brevis. It pierces the deep fascia at the 
junction of the distal and middle thirds of the leg, and is con- 
tinued on to the dorsum of the foot, to which it supplies some 
small cutaneous filaments. Its terminal branches supply the 
medial side of the hallux and the contiguous sides of the 
second, third, fourth and fifth toes (Fig. 73). 



THE SACRAL PLEXUS 



179 



The Peronceus Longus arises from the lateral aspect of the fibula and 
descends behind the lateral malleolus. It then passes forwards on the 
lateral aspect of the calcaneus below the trochlear process (peroneal 




A B 

Fig. 73. — The Nerve-supply of the Skin on the Anterior Aspect 
of the Lower Limb. 

A. The individual nerves of supply. 

B. The segmental supply. 



Lateral cutaneous nerve. 
Lumbo-inguinal nerve (crural branch 

of genito-crural nerve). 
Intermediate (middle) and medial 

cutaneous nerves. 
Obturator nerve. 



5. Lateral sural nerve. 

6. Saphenous nerve. 

7. Superficial peroneal(musculo-cutaneous) 

nerve. 

8. Medial branch of deep peroneal (an- 

terior tibial) nerve. 



tubercle), and, entering a groove on the plantar aspect of the cuboid, it 
passes across the sole of the foot to be attached to the base of the first 
metatarsal and the adjoining portion of the medial cuneiform bone. It 
bridges across the extremities of the transverse arch of the foot, and so 
constitutes a strong support (p. 176). 



180 THE NERVOUS SYSTEM 

The Peronaus Brevis has a similar origin, but it passes above the 
trochlear process and is inserted into the tubercle on the base of the fifth 
metatarsal bone. Both these muscles act as plantar flexors of the foot, 
but, at the same time, they elevate the lateral border of the foot from the 
ground, i.e. they act as powerful evertors. When they are brought into 
action, a distinct furrow is produced on the lateral aspect of the leg and, 
in the bottom of this furrow, the contracted muscular bellies can be felt. 
The tendons also can be palpated as they cross the lateral aspect of the 
calcaneus (os calcis), just distal to the lateral malleolus. 

The Deep Peroneal Nerve enters the anterior compartment 
of the leg and is, at first, very deeply placed. As it descends, 
it supplies branches to the neighbouring muscles and, opposite 
the ankle-joint, it divides into lateral and medial branches, 
which extend on to the dorsum of the foot. The lateral 
branch is mainly distributed to the extensor digitorum brevis, 
but the medial branch runs forwards to supply the contiguous 
sides of the hallux and second toe. 

The Tibialis Anterior forms the muscular prominence in the proximal 
part of the anterior compartment of the leg. It arises from the tibia and 
its tendon passes distally and medially, crossing the anterior aspect of the 
ankle-joint, to be inserted into the base of the first metatarsal and the medial 
cuneiform bone. The tibialis anterior acts as a powerful dorsi-flexor and, 
in company with the tibialis posterior, as a powerful invertor of the foot. 

The Extensor Hallucis Longus and the Extensor Digitorum Longus 
arise from the fibula and pass distally in front of the ankle-joint. The 
former is inserted into the base of the terminal phalanx of the hallux, and 
the latter divides into four tendons, which are inserted into the lateral four 
toes in the same manner as the tendons of the extensor digitorum com- 
munis in the fingers. 

Both these muscles dorsi-flex the foot in addition to extending the toes. 

The Peronceus Tertius arises from the distal part of the fibula and its 
fleshy belly is continuous with that of the extensor digitorum longus. It 
crosses the anterior aspect of the ankle-joint and is inserted into the dorsum 
of the base of the fifth metatarsal bone. Its principal action is to assist in 
dorsi-flexion of the foot, but it also helps in the movement of eversion. 

The Extensor Digitorum Brevis is a small muscle, which arises from the 
anterior part of the upper surface of the calcaneus (os calcis). When the 
toes are strongly extended, it forms a small elevation, a little in front of 
the lateral malleolus. It gives origin to four tendons, which pass to the 
medial four digits. 



THE SACRAL PLEXUS 



181 



Affections of the Sciatic Nerve or of its numerous 
branches are by no means uncommon. The main trunk is pro- 




9 - 



-5 
.6 



--■5 



9- 




Fig. 74. — The Nerve-supply of the Skin on the Posterior Aspect 
of the Lower Limb. 

A. The individual nerves of supply. 

B. The segmental supply. 



1. Posterior rami of L. 1,2 and 3. 

2. Posterior rami of S. i, 2 and 3. 

3. Sacro-coccygeal nerve. 

4. Iliac branch of ilio-hypogastric nerve. 

5. Posterior cutaneous nerve of thigh 

(small sciatic nerve). 



6. Lateral cutaneous nerve of thigh. 

7. Lateral sural nerve. 

8. Nervus suralis. 

9. Saphenous nerve. 

to. Medial cutaneous nerve of thigh. 
11. Obturator nerve. 



vided with a thick, fibrous sheath, winch is the site of inflamma- 



182 THE NERVOUS SYSTEM 

tion in sciatica. In this condition, the sciatic nerve is tender 
on deep pressure, and subjective symptoms are experienced over 
the distribution of its sensory branches, usually over the areas 
supplied by the lateral sural nerve and the nervus suralis 
(Fig. 74). When the nerve-sheaths are much thickened as 
the results of the inflammation, the cutaneous branches are 
nipped as they pierce the deep fascia, giving rise to the 
"tender points of Valleix." It should be observed that when 
the condition is due to a localised neuritis of the sciatic nerve, 
no subjective symptoms are felt in the skin area which is 
supplied by the posterior cutaneous (small sciatic) nerve (Fig. 
74). On the other hand, when the condition is due to intra- 
pelvic pressure, this area is quite likely to be affected. 

When the sciatic nerve is completely paralysed, the motor 
symptoms are very striking. All the muscles distal to the knee 
are paralysed, and movements of the ankle, foot and toes are 
quite impossible. In addition, the hamstring muscles are 
affected, but this does not produce such a striking change, as 
the knee can be flexed by means of the gracilis and the 
sartorius (obturator and femoral nerves, respectively). 

The amount of sensory loss is relatively smaller. The 
posterior aspect of the leg in its proximal part is supplied by 
the posterior cutaneous nerve of the thigh (small sciatic), and 
the medial aspects of the leg and foot are supplied by the 
saphenous nerve. As a result, the area of sensory loss is 
restricted to the lateral aspect of the leg, the dorsum of the 
foot, except near the medial border, and the sole of the foot. 
Despite the position of the lesion, deep sensibility is only 
affected in the distal part of the foot (Sherren). 

It is interesting to observe that, when the sciatic nerve is 
injured as the result of stab or gunshot wounds, the fibres 
affected are in 90 per cent, of cases (Makins) those of the 
peroneal portion of the nerve, but no adequate explanation 
can yet be offered to account for this peculiarity. 

The Posterior Cutaneous (Small Sciatic) Nerve of the thigh 
(S. 1, 2 and 3) arises from the posterior aspect of the 



THE PUDENDAL PLEXUS 18 



o 



sacral plexus and enters the buttock through the great 
sciatic foramen. Beyond the lower border of the glutaeus 
maximus, the nerve descends immediately under the deep 
fascia. It supplies branches to the skin on the posterior 
aspect of the thigh, over the popliteal fossa, and over the 
proximal part of the posterior aspect of the leg. This nerve 
is derived from segments of the spinal medulla which are 
accustomed to receive impulses via the sympathetic from the 
lower part of the rectum and the upper part of the anal canal, 
and from the internal trigone of the bladder. In most cases 
in which a " focus of irritation" (p. 195) is established in the 
mid-sacral region of the spinal medulla, the referred pains are 
experienced in the perineum, but in some cases the pain is 
referred to the posterior aspect of the thigh, and the condition 
may be mistaken for sciatica, unless the sciatic nerve is 
subjected to local examination by deep pressure. 

THE PUDENDAL PLEXUS 

The Pudendal Plexus is formed by portions of the second, 
third and fourth sacral nerves. Like the sacral plexus, it lies 
in front of the sacrum and behind the rectum, and it is 
therefore subject to the same varieties of intra-pelvic pres- 
sure (p. 171). 

The Pudendal (Internal Pudic) Nerve (S. 2, 3 and 4) is the 
most important branch of the pudendal plexus. It arises in 
the pelvis and enters the lateral wall of the ischio-rectal fossa, 
where it gives off the inferior hemorrhoidal nerve, and divides 
into the perineal nerve and the dorsal nerve of the penis (or 
clitoris). 

The Inferior Hemorrhoidal Nerve is distributed to the 
external sphincter muscle and to the skin around the anus. 
In the condition of anal fissure, the external sphincter 
becomes refiexly contracted owing to the tearing of the 
mucous membrane, which receives its nerve-supply from the 
same source (p. 284). 



1 84 THE NERVOUS SYSTEM 

The Perineal Nerve contains both motor and sensory 
fibres. The former supply the levator ani and the muscles of 
the urogenital triangle of the perineum, i.e. the sphincter 
(compressor) urethras, the ischio- and the bulbo-cavernosus 
(the erector penis and the ejaculator urinae) and the transverse 
perineal muscles. The sensory fibres supply the skin of the 
perineum anterior to the anus, including the skin of the 
scrotum. In addition, they supply the bulb of the penis and 
the corpora cavernosa. 

The Dorsal Nerve of the Penis supplies the whole of the 
skin covering the penis, including the deep surface of the 
prepuce and the surface of the glans. 

Referred pain may be experienced in the perineum, scrotum 
and penis, in pathological conditions of the viscera which are 
innervated by the sacral segments of the spinal medulla. 
It is especially common in vesical calculi, but it also occurs in 
inflammatory or irritative conditions of the lower part of the 
rectum, the anal canal, the prostate and the seminal vesicles. 

The Perforating Cutaneous Nerve (S. 2 and 3) pierces the 
sacro-tuberous (great sacro-sciatic) ligament and the lower 
border of the glutaeus maximus, and supplies the skin of the 
buttock in the neighbourhood of the coccyx. 

The Perineal Branch of the Fourth Sacral helps to supply 
the external sphincter. 

In addition to the named branches, the pudendal plexus 
gives off branches of supply to the levator ani and the 
coccygeus. These two muscles form the floor of the pelvis 
and shut it off from the ischio-rectal fossae. The levatores 
ani arise from the pelvic wall and project downwards and 
inwards to meet one another. They are attached to a median 
raphe, which extends from the tip of the coccyx to the 
posterior aspect of the anal canal, and they constitute a 
muscular bed on which the terminal part of the rectum lies as 
it runs horizontally forwards (p. 283). The anterior fibres, which 
arise from the pelvic surface of the pubis, pass downwards and 
backwards ; some of them blend with the muscular wall of 






THE SYMPATHETIC SYSTEM 185 

the anal canal, while others pass lateral to the rectum and 
support the angle of union between the rectum and the anal 
canal. When the levator ani contracts, it forms an unyielding 
floor against which the pelvic viscera may be compressed by 
the action of the abdominal muscles during defalcation. 
Further, the anterior fibres hold the anal canal steady, when 
a faecal mass is passing through it. 

THE SYMPATHETIC NERVOUS SYSTEM 

The sympathetic nervous system is subsidiary to the central 
nervous system, and the fibres which it distributes and the 
fibres which it receives are governed ultimately by nerve-cells 
in the cerebral cortex. 

The system consists of two trunks {cords), one on each side 
of the body, which extend through the neck, thorax, abdomen 
and pelvis, and each trunk possesses numerous ganglia, which 
are interconnected by nerve-fibres. A typical ganglion corre- 
sponds to one segment of the spinal medulla artd is connected 
to the anterior ramus (primary division) of the spinal nerve 
of that segment by means of a grey ramus communicans. 

The grey rami communicantes contain fibres which are 
passing from the sympathetic to the spinal nerves. When they 
reach the nerve, some of the fibres pass centrally to the spinal 
medulla, while others pass peripherally to be distributed by 
the nerve to the blood-vessels, sweat glands, etc. Efferent 
fibres from the central nervous system to the sympathetic do 
not run in the grey rami. They are found in the ivhite rami 
communicantes, which are limited to certain ganglia. 

The white rami communicantes connect T. 1 or 2 - L. 1 or 
2 and S. 2, 3 and 4 with the corresponding sympathetic 
ganglia, and, in addition to efferent fibres, they contain the 
afferent fibres from the viscera. They are not present in the 
cervical region, and, therefore, the fibres which are distributed 
by the cervical ganglia must descend through the cervical 
portion of the spinal medulla and join the sympathetic via the 



1 86 



THE NERVOUS SYSTEM 



highest white ramus (T. i or T. 2, as the individual case may 
be). It follows, therefore, that in complete lesions of the spinal 
medulla above the first thoracic segment, the whole of the 
sympathetic system is cut off from the controlling influence of 
the cerebral cortex. 




Fig. 75. — Diagram of the Sympathetic Nervous System. 

Efferent fibres from the spinal medulla to the sympathetic are shown in blue. 
Afferent sympathetic fibres are shown in red. 



1. Afferent sympathetic fibres. 

2. Efferent sympathetic fibres. 

3. Posterior nerve-root of T. 2. 

4. Anterior nerve-root of T. 2. 

5. Efferent sympathetic fibres ascending 

cervical part of sympathetic trunk. 



6. Grey ramus communicans. 

7. Inferior cervical ganglion. 

8. Cardiac branch from 7. 

9. White ramus communicans. 

10. Anterior ramus (primary division) 
ofT.2. 



In the cervical region, the sympathetic ganglia are three in 
number. The superior cervical ganglion communicates with the 
upper four cervical nerves by means of grey rami communicantes. 
It distributes branches to all the blood-vessels, sweat glands, 
salivary glands, etc., of the head and neck. Some of these 
branches issue from the upper end of the ganglion and enter 



THE SYMPATHETIC SYSTEM 187 

the interior of the skull in company with the internal carotid 
artery. The most important of these join the semilunar 
(Gasserian) ganglion and are carried by the naso-ciliary branch 
of the ophthalmic nerve (p. 66) to the ciliary ganglion, from 
which they pass forwards to the eyeball to supply the dilator 
muscle of the pupil. Paralysis of this muscle is an important 
sign in affections of the sympathetic (p. 189). 

The middle and inferior cervical ganglia give off grey rami 
communicantes, which join the fifth and sixth and the seventh 
and eighth cervical nerves, respectively. In this way, the 
blood-vessels and sweat glands of the upper limb are brought 
under the control of the sympathetic system. 

In addition, each cervical ganglion gives off a cardiac branch 
and these branches constitute the accelerator nerves of the heart 
(p. 308). 

The sympathetic trunk enters the thorax by crossing the 
anterior aspect of the neck of the first rib and then descends 
in front of the heads of the ribs. It posseses eleven or twelve 
thoracic ganglia, and each of these is connected to the inter- 
costal nerve to which it corresponds by both a white and a 
grey ramus communicans. As already stated, the white rami 
contain efferent fibres from the spinal medulla to the sym- 
pathetic system, and they occur throughout the thoracic region, 
with the occasional exception of the first thoracic segment. 
These efferents from the spinal medulla have to supply a 
very large area, since there are no white rami communicantes 
in the cervical or in the lower lumbar region. They ascend 
through the cervical part of the sympathetic trunk, through 
which they are distributed to the head and neck and upper 
limb. 

Other sympathetic efferents arise from the thoracic ganglia 
and pass to be distributed to the contents of the abdomen. 
They form the splanchnic nerves and the largest of them 
receives branches from the fifth to the tenth thoracic ganglia, 
inclusive. The smaller splanchnic nerve arises from the 
tenth and eleventh and the smallest from the eleventh ganglion. 



1 88 THE NERVOUS SYSTEM 

The greater and smaller splanchnics descend through the 
thorax and pierce the crus of the diaphragm. On the 
abdominal surface of the latter, they join the large cceliac 
(semilunar) ganglion, which is a subsidiary sympathetic ganglion. 
The two cceliac ganglia are connected to one another by 
numerous branches, which are closely associated with the 
cceliac artery and its branches. From the ganglia visceral 
branches arise and travel on the coats of the arteries to be 
distributed to the abdominal viscera. The precise innervation 
of the viscera is dealt with under the individual organs. 

In the abdomen, the sympathetic trunk lies on the sides of 
the bodies of the lumbar vertebrae. There are usually five 
lumbar ganglia, and, while each possesses a grey ramus 
communicans, only the first and, sometimes, the second 
possess white rami communicantes. Most of the efferent 
fibres of the latter are carried off by the femoral and obturator 
nerves to supply the blood-vessels, etc., of the lower limb, 
while others have a similar distribution in the walls of the 
abdomen. 

In the pelvis, the sympathetic trunks lie in front of the 
sacrum, medial to the anterior sacral foramina, and in front of 
the coccyx they unite with one another in the gang/ion impar. 
There are usually five sacral ganglia and, though each possesses 
a grey ramus communicans, the white rami are restricted to 
the second and third, or, in some cases, to the third and 
fourth ganglia. 

A large plexus is developed in connection with the sym- 
pathetic in front of the promontory of the sacrum. It is 
termed the hypogastric plexus and it is formed by (i) fibres 
from the aortic plexus, which is a downward continuation of 
the plexus connecting the cceliac ganglia; (2) branches from 
the lumbar ganglia ; (3) branches from the sacral ganglia. By 
means of this plexus the white rami communicantes of the mid- 
sacral region are distributed to the pelvic viscera, the rectum, 
anal canal, bladder, prostate, etc. 

Lesions of the Sympathetic System fall into two groups. 



THE SYMPATHETIC SYSTEM 189 

In the first, the lesion affects the spinal medulla, and the 
sympathetic and the cerebrospinal systems are involved 
together. With regard to both systems, the amount of 
paralysis depends on the nature and the level of the lesion. 
The whole of the sympathetic system is paralysed in complete 
lesions of the spinal medulla above the level of the first 
thoracic segment, but the amount of paralysis is much less when 
the injury occurs in the thoracic or lumbar regions (p. 190). 

In the second group, the sympathetic trunk is itself involved. 
The lesion is usually due to the pressure of a tumour growth 
and is consequently unilateral in most cases. 

(a) When the sympathetic trunk is involved between the 
superior and the middle cervical ganglia, the sympathetic 
supply to the head and neck is entirely cut off and the condi- 
tion gives rise to certain well-marked and easily recognisable 
symptoms, of which the most important are those in connec- 
tion with the eye. ( 1 ) The dilatator pupillas muscle is paralysed 
and the pupil on the affected side is therefore definitely con- 
tracted. (2) In addition, owing to paralysis of the ciliary 
bundle (p. 210), pseudo-ptosis develops together with 
apparent narrowing of the palpebral fissure. (3) These 
features are accompanied by a slight degree of enophthalmos, 
for which no very satisfactory explanation has yet been brought 
forward. (4) All the blood-vessels of the affected side of the 
head and neck become dilated, and the resulting vascular 
engorgement is seen best in the conjunctiva. (5) The salivary 
and lacrimal secretions are usually increased in quantity in the 
first instance, but they may be deficient or even absent at a 
later period. (6) The affected areas of skin become dry and 
rough, owing to paralysis of the sweat-secreting glands. 

It should be remembered that tumour pressure at first pro- 
duces an irritative lesion, causing stimulation rather than 
paralysis of the sympathetic. In this event, the above- 
described chain of symptoms is reverstd. The pupil is widely 
dilated, the skin areas sweat profusely, etc. 

(b) Lesions occurring at the middle cervical ganglion, or 



1 9 o THE NERVOUS SYSTEM 

between it and the inferior cervical ganglion, produce precisely 
the same symptoms as in (a), but, in addition, the blood- 
vessels and sweat glands of a part or parts of the upper limb 
are affected. 

(c) Lesions occurring at the inferior cervical gang/ion, or 
between it and the first thoracic ganglion (or the second, as 
the case may be), cut off the sympathetic supply of the whole 
of the upper limb and of the head and neck, on the same side. 

(d) Lesions affecting the sympathetic trunk in the thoracic 
region only involve the particular segment or segments in 
which they are situated, as each ganglion possesses its own 
white ramus communicans. They therefore produce no char- 
acteristic or widespread symptoms. 

(e) In the same way, lesions occurring in the lumbar or 
sacral part of the sympathetic trunk are definitely limited in 
their effects to the regions supplied by the ganglia involved. 

In the abdomen, however, the cceliac ganglia and plexus 
(p. 1 88) may not only be affected by tumours in connexion 
with the viscera in their neighbourhood, but they themselves 
may be the site of tuberculous disease. Certain cases of 
Addison's disease have been recorded in which, at the subse- 
quent post-mortem examination, such a condition was found 
to be present, while the supra-renal glands were perfectly 
normal (p. 408). 

Referred Pain 

The Viscero-sensory Reflex. — It has been recognised for 
many years that painful sensations may be experienced in some 
area or areas remote from the exciting cause, but it is only 
recently that the importance of such referred pains has been 
realised. 

The simplest instances of referred pain are found when 
stimulation of one sensory branch of a spinal nerve produces 
painful sensations in the area supplied by another sensory 
branch of the same nerve. The classical example occurs in 
tuberculous disease of the hip-joint. In this case the patho- 



REFERRED PAIN 



191 



logical process stimulates the articular branches of the femoral 
(anterior crural) nerve, but the pain of which the patient 
complains is referred to the region of the knee, which also 
receives branches from the same nerve (Fig. 73). 

It is by no means certain by what sequence of events a 
referred pain is produced. Mackenzie, to whom we are 
indebted for most of our knowledge on this subject, suggests 




Fig. 76. — Diagram to explain a Viscerosensory Reflex. 

The plain arrows indicate the path of afferent impulses from the viscus ; the 
dotted arrows indicate the "overflow" stimulus. 



C. Cortex. 
P.tt.r, Posterior nerve-root. 
ll'.R.C. White ramus communicans. 



G.R.C. Grey ramus communicans. 
Sy. G. Sympathetic ganglion. 
/'. Viscus. .S". Skin. 



that abnormal afferent impulses may not only stimulate the 
nerve cells for which they were originally intended, but may 
" overflow : ' and so stimulate other nerve-cells in their neigh- 
bourhood. The effect produced by this " overflow " stimula- 
tion will be the same as if the cells had received an impulse 
from the nerve-fibres with which they are associated. In both 
methods of stimulation, the impulse which ascends to the cortex 
is interpreted in the same way and, if the cells affected by the 
"overflow" normally receive afferent stimuli from a cutaneous 



i 9 2 THE NERVOUS SYSTEM 

nerve, the interpretation will be a painful sensation in the area 
supplied by that nerve. It is at present impossible to say 
whether this theory is correct or not, but at least it offers a 
reasonable working hypothesis. 

A precisely similar sequence of events may occur in con- 
nexion with any of the sensory cerebral nerves. Thus, 
stimulation of one of the terminal branches of the inferior 
alveolar (dental) nerve by an abscess at the root of a tooth 
may produce not only toothache but also referred pain in the 
external acoustic (auditory) meatus (auriculotemporal nerve, 

P- 75)- , . , 

Referred pains may be excited not only by pathological 

processes affecting structures supplied by cerebro-spinal nerves, 
but also in the case of structures which receive their nerve- 
supply from the sympathetic system. For example, in attacks 
of angina pectoris the pain frequently spreads from the prae- 
cordia to the medial side of the upper limb, and, in rare 
cases, it may commence in the upper limb and spread to the 
chest. The pain in the upper limb is unquestionably a 
referred pain and it may be accounted for by the " overflow " 
hypothesis. Afferent impulses from the heart pass via the 
sympathetic to the spinal medulla, where they terminate in 
connexion with nerve-cells in the upper thoracic segments 
(p. 307). These segments also contain the cells which 
receive afferent sensory impressions from the medial side of 
the arm. Under normal conditions the afferent impulses from 
the heart do not "overflow," but, in angina pectoris, the 
impulses are abnormal in character and they "overflow" so 
as to stimulate those neighbouring nerve-cells which are con- 
cerned in the cutaneous supply of the medial side of the 
upper limb. To this sequence of events Mackenzie has given 
the name of " viscero-sensory reflex." 

It is clear that viscera may give rise to referred pains, and 
it is therefore important to differentiate, if possible, between 
referred pains and pains actually experienced in the viscera 
themselves, but attempts to do so meet with numerous 



REFERRED PAIN 193 

difficulties. Muscles and fasciae, though not so acutely 
sensitive as the skin, may be the site of painful sensations and, 
therefore, abdominal pain felt on a deeper level than the 
skin is not necessarily experienced in an abdominal viscus. 
Mackenzie has come to the conclusion that the viscera them- 
selves are insensitive to painful stimuli and that they can 
only give rise to pain through a viscerosensory reflex. He 
has been able to adduce a large mass of evidence in support 
of this view, but it is opposed by evidence which is difficult 
to controvert. 

The investigation of the question is necessarily carried out, 
for the most part, on patients who are quite devoid of 
anatomical knowledge, and the difficulty they experience in 
localising abdominal pains is increased thereby. This 
difficulty is caused by the presence of the abdominal walls, 
which conceal the viscera, and by the absence in the viscera 
of any sense corresponding to the muscle and joint sense in 
the limbs. A healthy person is not conscious of his viscera, 
as the nervous mechanism which controls them is, for the 
most part, entirely automatic. On the other hand, a healthy 
person is always conscious of the position of those parts of the 
body which are supplied by cerebro-spinal nerves. If one 
attempts to localise the exact position of a painful area in the 
hand through a piece of wood or some other solid object, it 
is found that such localisation, though aided by muscle and 
joint sense, is by no means accurate. In the light of this 
experiment, one can appreciate the difficulty of localising an 
abdominal pain, if one assumes that the pain is felt only in 
the viscus and that the sensibility of the abdominal wall is 
not affected. Consequently, when a painful area indicated 
by a patient does not exactly correspond in size or position 
to the viscus in which it is supposed to originate, it does 
not necessarily follow that the pain is not felt in the viscus 
itself. 

Further, many medical men, who have suffered from colitis 
or some other painful condition of the large intestine, state 
1.1 



i 9 4 THE NERVOUS SYSTEM 

with confidence that they can trace the pain from the caecum 
to the rectum, and that it follows the actual course of the 
bowel. 

On the other hand, cases in which abdominal operations 
have been performed without the use of a-general anaesthetic 
show that the viscera may be clamped, cut or sutured without 
giving rise to any painful impressions. In a case operated on 
by Mackenzie without an anaesthetic of any kind, the patient 
suffered pain periodically, and it was observed that the pain 
synchronised with peristalsis affecting a clamped portion of 
small intestine. The patient, however, localised the pain to 
an area of the abdominal wall several inches removed from 
the piece of gut in question. It seems highly probable that 
this was an example of the viscero-sensory reflex, although it 
is possible that the mal-reference by the patient was owing to 
lack of localising sense. 

The arm pain in angina pectoris (p. 309) and the testicular 
pain in renal colic (p. 364) are both undoubtedly referred 
pains, and it is not illogical to assume that the chest pain in 
the former and the abdominal pain in the latter are of a 
similar nature. 

The relation which exists between the nerve-supply of the 

viscera and the nerve-supply of the skin of the trunk is a 

further argument in favour of Mackenzie's view that the 

viscera are insensitive to painful stimuli. When the segments 

of the spinal medulla which are responsible for the sensory 

supply of the skin of the thoracic and abdominal parietes 

are compared with those which are connected with the 

sympathetic system by means of white rami communicantes 

(p. 185), it is found that they are practically identical. The 

lower lumbar nerves give off no white rami to the sympathetic 

and they are not represented in the skin-supply either of the 

abdominal wall proper or of the perineum, which forms a 

part of the abdominal wall. Further, only those sacral nerves 

which possess white rami communicantes take part in the 

sensory supply of the perineum and the external genitalia. 



REFERRED PAIN i 95 

This relationship between the nerve-supply of the skin of the 
trunk and the nerve-supply of the viscera suggests a very 
intimate connexion between the viscera and the covering 
parietes. 

It may be pointed out that viscera which contain muscle 
fibres give rise to pain of much greater severity and with much 
more frequency than viscera which contain few or no muscle 
fibres. A striking contrast exists between the intense pain 
which may be caused by a minute calculus in the pelvis of 
the ureter and the entire absence of pain in advanced disease 
of the liver, lungs or kidneys. 

Enough has been said to make it clear that any viscus may 
give rise to the viscero-sensory reflex, and it is equally clear 
that our knowledge of this important subject is as yet very 
deficient. 

"A Focus of Irritation." — When a viscero-sensory reflex 
is established in connexion with a pathological process in 
a viscus, the stream of abnormal afferent impulses from that 
viscus and the constant " overflow " may cause a temporary 
increase in the excitability of the nerve-cells secondarily 
affected. This condition has been termed by Mackenzie 
a "focus of irritation." As a result of the increased excit- 
ability, an exaggerated interpretation is given to ordinary 
stimuli passing through the affected cells. For example, if a 
" focus of irritation " is set up in the eighth thoracic segment 
by a gastric ulcer, the result may be an increase in the 
excitability of the nerve-cells which are accustomed to receive 
impulses from the terminal branches of the eighth intercostal 
nerve. When this is the case, it is found that an area of 
cutaneous hyperalgesia is present in the epigastric region, 
i.e. gentle stroking of the skin over a certain area gives rise 
to a feeling of discomfort or pain, because the afferent impulse 
from the skin becomes exaggerated in its passage through 
the cells which are in a state of increased excitability. The 
discovery of such an area is of value, because, when the 
spinal nerve which supplies it is known, the site of the 



196 THE NERVOUS SYSTEM 

"focus of irritation " can be determined and this will help 
to identify the viscus at fault. 

Owing to the limited extent of the spinal medulla, the visceral 
centres are not placed each in a separate segment, so that two or 
more visceral centres may occupy the same segment or series of 
segments. For example, the centre for the stomach is situated in 
the fifth to the eighth thoracic segments, while that for the liver 
and gallbladder occupies the seventh to the tenth thoracic seg- 
ments. Consequently, when a " focus of irritation " arises in the 
seventh and eighth thoracic segments, owing to a pathological 
condition of the gall-bladder, the adjoining cells of the centre for 
the stomach may be thrown into a condition of increased excit- 
ability. In this event the afferent impulses which ascend from 
the stomach after the ingestion of food become altered as they 
pass through the "focus of irritation." As a result, although 
the stomach itself is perfectly healthy, food may be vomited 
immediately after it has been taken. Similarly, a "focus of 
irritation " in the lower thoracic region may account for 
frequency of micturition in some cases of appendicitis. 

It must be remembered that the viscera acquire their nerve- 
supply at an early period of their development and, therefore, 
those viscera which develop in the median plane are innervated 
by both sides of the spinal medulla. At a later date, certain 
of these viscera, e.g. the stomach, take up a permanent position 
to one side of the median plane, while others, e.g. the coils of 
small intestine, vary in position from time to time. It would 
appear that, in the former case, the viscus loses, or neglects to 
use, the nerves from the opposite side of the spinal medulla, 
whereas, in the latter case, the innervation from both sides is 
retained. As a result, referred pains from the stomach, gall- 
bladder, etc., are not experienced in the median plane, as they 
are in the case of the small intestine. It is impossible, how- 
ever, to be dogmatic upon this aspect of the subject, as our 
present knowledge is very incomplete. 

Viscera which develop to one side of the median plane, e.g. 
the ureters, are innervated from the same side of the spinal 



REFERRED PAIN 197 

medulla, and, when they give rise to referred pain, the pain 
is always experienced on the same side of the body and never 
spreads to the opposite side. 

The Viscero-motor Reflex. — Pathological processes which 
give rise to pain are frequently accompanied by muscular 
contractions. This association is well seen in tuberculous 
disease of the cervical vertebrae, in which the rigidity of the 
muscles of the back of the neck is a striking feature. The 
muscular contraction is quite involuntary, and it may be 
explained as a result of the "viscero-motor reflex" of 
Mackenzie. 

In order to account for the viscero-motor reflex, it is 
necessary to assume that the afferent pathological impulses 
"overflow" so as to affect the cells round which the fibres 
of the pyramidal tract (p. 37) arborise. This "overflow" 
stimulus produces precisely the same results as a stimulus 
arising in the motor cortex, and it affects the motor nerves 
which arise from the segment of the spinal medulla in which 
the " focus of irritation " is situated. 

The viscero-motor reflex may be observed in the case of 
structures innervated through the sympathetic system, and 
many examples can be brought forward. The board-like con- 
traction of the muscular abdominal wall in cases of acute 
general peritonitis, the localised contraction of the upper part 
of the right rectus abdominis in cholecystitis (p. 265), the 
contraction of the cremaster in renal colic (p. 364), are all 
instances of this condition. 

Particular examples of the viscero-sensory and viscero-motor 
reflexes are detailed in the sections dealing with the individual 
viscera (see Stomach, Ureter, Bladder, etc.). 



II 

THE ORGANS OF SPECIAL SENSE 

The organs of special sense include the nose, the ear and the 
eye. 

The Ear, or Organ ok Hearing, 

consists of three parts, namely — (i) The Auricle and the 
External Acoustic Meatus, (2) the Cavum Tympani or 
Middle Ear, and (3) the Internal Ear. 

The skin of the Auricle receives its nerve-supply from two 
quite different sources. Its postero-inferior part is supplied 
from the cervical plexus through the great auricular nerve 
(C. 2, 3), but its antero-superior part is supplied from the fifth 
cerebral nerve through the auriculotemporal branch of the 
mandibular division (Fig. 40). 

The External Acoustic Meatus is about 1 inch in length, 
and is partly cartilaginous and partly osseous. At its medial 
extremity the meatus is closed by the tympanic membrane, 
which is set obliquely so that its lateral surface is directed 
forwards and downwards as well as laterally. Examination 
of the membrane by reflected light is rendered more difficult 
on account of the bends which occur in the meatus. The 
cartilaginous portion, which forms the lateral third, passes 
medially, forwards and upwards ; the lateral part of the 
osseous portion passes medially and backwards, while the rest 
of the canal is directed medially, forwards and slightly down- 
wards. In order to obtain the best possible view of the 

membrane, it is necessary to bring the movable cartilaginous 

198 






THE EAR 199 

portion into line with the lateral part of the osseous portion, 
and this can be effected by dragging the auricle upwards and 
forwards. 

In the young child the osseous portion of the meatus is 
very short and the downward direction of the lateral surface 
of the membrane is more marked than it is in the adult. 

The narrowest part of the meatus is placed at about one- 
third of an inch from the membrane, and foreign bodies which 
succeed in passing beyond this point may only be removed 
with difficulty. The whole of the meatus is covered by a 
cuticular lining, which is firmly adherent both to the cartil- 
aginous and to the osseous walls, and, on this account, 
furuncles in the meatus are a source of very acute pain. 

The cerumen, or ear-wax, is secreted by the modified sweat 
glands of the cuticular lining and it is normally worked to 
the exterior by the movements of the mandibular condyle, 
which lies below and in front of the cartilaginous meatus. 
If the finger is placed in the external acoustic meatus and 
the mouth is alternately opened and closed, the effect of the 
movements of the condyle on the lumen of the meatus can 
be readily demonstrated. 

The cuticular lining of the meatus, which also covers the 
lateral aspect of the tympanic membrane, is supplied, almost 
entirely, by branches from the auricula-temporal nerve. The 
postero-inferior part of the membrane and the adjoining parts 
of the meatus, however, receive additional supply from the 
auricular branch of the vagus (p. 96). Referred pain in the 
external acoustic meatus may be due to irritation of any of 
the terminal branches of the trigeminal nerve, but it is most 
commonly associated with inflammatory conditions of the 
teeth of the mandible and consequent stimulation of the 
inferior alveolar (dental) nerve (p. 75). Similar pain may 
occur as the result of stimulation of terminal branches of 
the vagus, but this condition is by no means common. 
Further, not only may the meatus be the site of referred pain, 
but pathological conditions in the meatus may give rise to 



200 THE ORGANS OF SPECIAL SENSE 

referred symptoms in the distribution of the trigeminal or of the 
vagus nerve. In this way a small piece of inspissated ear-wax 
may be sufficient to set up a "focus of irritation" (p. 195) 
in the nucleus of the vagus, and so give rise to intractable 
coughing or chronic dyspepsia. 

In syringing the external acoustic meatus for the removal of 
cerumen, foreign bodies, etc., the nozzle of the instrument 
should be inserted at the postero-superior quadrant, so that it 
does not impede the outflow of the fluid employed. 

Otoscopic examination will be dealt with when the tympanic 
membrane is described. 

The Cavum Tympani, or Middle Ear, is an air-space in 
the interior of the petrous portion of the temporal bone. 
Anteriorly, it communicates with the nasopharynx through 
the auditory (Eustachian) tube, while, posteriorly, it opens 
into the tympanic {mastoid) antrum. These three structures 
are all lined with muco-periosteum, which is directly con- 
tinuous with the mucous membrane lining the pharynx. That 
part of the middle ear which lies above the upper border of 
the tympanic membrane is termed the epitympanic recess (attic). 

Suppurative conditions of the middle ear are of frequent 
occurrence, especially following the exanthemata, and on this 
account the relations of the cavity are of great importance. 

The roof of the middle ear is formed by a moderately thin 
plate of bone, termed the tegmen tympani, which separates the 
cavity from the middle fossa of the skull and the temporal lobe 
of the brain. Upward spread of septic processes in the middle 
ear may give rise to meningitis or extra-dural abscess (i.e. 
between the tegmen tympani and the dura mater), or it may 
lead to the formation of an abscess in the temporal lobe of 
the brain. (Forty per cent, of all cerebral abscesses occur in 
the temporal lobe and can be referred to this cause.) 

The floor of the middle ear is formed by a plate of bone, 
which separates the cavity from the jugular foramen and the 
commencement of the internal jugular vein. The latter 
structure may become the site of a septic thrombosis, if down- 



THE EAR 



201 



ward spread occurs in the course of a middle ear infection, 
and the clot may extend along the vein so that it can be felt 
on palpation at the upper part of the anterior border of the 
sterno-mastoid. \ 

The anterior wall of the middle ear is occupied, in its lateral 




FlG. 77. — Section through the Auricle, the External Acoustic Meatus 
and the Tympanum. (Turner's Anatomy.) 



a. Helix. 

b. Antitragus. 

c. Antihelix. 

d. Concha. 

e. Lobule. 

f. Mastoid process. 

g. Facial nerve. 

h. Styloid process. 



k. Internal carotid artery. 

/. Auditory (Eustachian) 
tube. 

in. Apex of petrous tem- 
poral. 

«. External acoustic 
meatus. 

o. Tympanic membrane. 



p. Tympanum. 

1. Malleus. 

2. Incus. 

3. Stapes. 

4. Cochlea. 

5. 6, 7. Semicircular canals. 

8. Facial nerve. 

9. Acoustic nerve. 



part, by the opening of the auditory {Eustachian) tube. The 
connexion thus established with the naso-pharynx ensures 
equality in the air pressure on the two sides of the tympanic 
membrane. Obstruction of the auditory tube, such as occurs 
in the condition of adenoids (p. 330), is followed by the 



202 THE ORGANS OF SPECIAL SENSE 

gradual absorption of the air in the middle ear, and, as the 
atmospheric pressure on the outside of the membrane is un- 
opposed, the membrane is bulged medially. Under these 
circumstances, the conduction of sounds to the internal ear 
is gravely disturbed. Artificial inflation of the middle ear, 
whether by Valsalva's method or by means of a Eustachian 
catheter (p. 329), is carried out for the purpose of equalising 
the pressure on the two sides of the tympanic membrane. 

In its medial part, the anterior wall separates the middle 
ear from the canal which contains the internal carotid artery. 
Cases have been recorded in which this portion of the wall 
has become necrosed, following otitis media, and the patient 
has died from the resulting haemorrhage. 

The posterior wall of the middle ear communicates with the 
tympanic (mastoid) antrum through an opening situated in its 
upper part. Suppurative processes beginning in either of the 
two cavities soon spreads to involve the other. 

The lateral wall of the middle ear is formed by the 
tympanic membrane and, above its upper border, by a small 
part of the squamous portion of the temporal bone. 

The Tympanic Membrane consists of three layers, which 
form an outer cuticular, a middle fibrous, and an inner 
mucous stratum. It presents a very intimate relation to the 
malleus, the head of which, however, lies in the epitympanic 
recess (attic) above the level of the membrane. The handle 
of the malleus passes downwards and slightly forwards between 
the fibrous and mucous strata, and its outline can be deter- 
mined on otoscopic examination. At its upper part, the 
handle of the malleus is crossed by the chorda tympani 
nerve (p. 84), which emerges from a small canal in the 
posterior wall and passes forwards to the anterior border of 
the membrane, where it enters another canal, which conducts 
it to join the lingual nerve (p. 75). 

On Otoscopic Examination the handle of the malleus can 
be distinctly seen, and from its lower end, which lies a little 
below the centre of the membrane, a " cone of light " passes 



THE EAR 203 

downwards and forwards over the anteroinferior quadrant of 
the tympanic membrane (Fig. 78). 

Posterior to the handle of the malleus the shadow of the 
long process of the incus may be made out. It is parallel to 
the former but lies on a slightly deeper plane, and is not in 
direct contact with the membrane. As a result, it can only 
be observed under favourable conditions. 

The " cone of light " is taken as a guide when the operation 
of paracentesis is carried out for the evacuation of pus from 
the middle ear. The incision is made immediately posterior to, 
and on a level with, the " cone of light," so that it passes 



Crus longum 
of incus 



Malleus 



Site for para- 
centesis tympani 



Fig. 78. — Lateral Aspect of Right Tympanic Membrane. 
Note. — The "cone of light" occupies the anteroinferior quadrant of the membrane. 

through the postero-inferior quadrant. This area is chosen, as 
it is well removed from the ossicles and the chorda tympani. 
Further, on account of the obliquity of the membrane, good 
drainage is afforded by an opening in this position. 

The medial wall of the middle ear is formed by a part of 
the petrous portion of the temporal bone, and it separates the 
cavity from the internal ear. Nearly the whole extent of this 
wall is occupied by a well-marked elevation, termed the 
promontory, which is produced by the first coil of the cochlea. 
At the postero-superior corner of the promontory, the foot- 
piece of the stapes fills in an oval aperture in the bone and it 
is in contact with the perilymph of the internal ear. At the 




204 



THE ORGANS OF SPECIAL SENSE 



postero-inferior corner of the promontory, there is a small 
circular foramen, termed the fenestra cochlea {rotunda), which 
is closed by a membrane. This membrane intervenes between 
the middle ear and the perilymph of, the cochlea (p. 207), 
and it lies practically opposite to the postero j inferior quadrant 
of the membrana tympani. As the middle ear is normally 
rather less than one-eighth of an inch wide at this point, in 
performing paracentesis care must be taken lest the point of 




Fig. 79. — The Facial Nerve traversing ihe Facial Canal in the Petrous 
Part of the Temporal Bone. 

11. Facial nerve. 

the instrument pass across the middle ear and open into the 
labyrinth. 

The facial canal, which transmits the facial nerve through 
the petrous portion of the temporal bone, passes backwards 
above the promontory. As the bony wall which separates it 
from the cavity of the middle ear is extremely thin, it may 
readily become necrosed in the course of otitis media, ex- 
posing the facial nerve and leading to facial paralysis (p. 87). 

Two small muscles, termed the tensor tympani and the 



THE EAR 205 

stapedius, are found in the middle ear. The former occupies 
a small bony canal, placed just above the auditory (Eustachian) 
tube, and passes backwards to be inserted into the upper end 
of the handle of the malleus. As the tensor tympani 
approaches its insertion, it winds round a small bony process, 
termed the processus cochleariformis, so that, when it con- 
tracts, it draws the handle of the malleus in a medial direction, 
and thus increases the normal slight concavity on the lateral 
surface of the tympanic membrane. In this way the membrane 
is rendered tense. The muscle receives its nerve-supply from 
the otic ganglion (p. 70), but it is believed that the fibres 
originate in the nucleus of the facial nerve and are conveyed 
to the ganglion by the lesser superficial petrosal nerve (p. 92) 
(Sahli). 

The stapedius arises within the posterior wall of the middle 
ear and passes forwards to be inserted into the neck of the 
stapes. The precise action of the stapedius is somewhat 
doubtful, but it has been suggested that it is antagonistic to 
the tensor tympani. On this supposition, it is clear that 
paralysis of the stapedius will lead to the condition of 
hyperacousis (p. 80), since the tensor tympani is no longer 
opposed. The stapedius receives its nerve-supply from a 
small branch of the facial nerve. This branch arises as the 
facial nerve descends to reach the stylo-mastoid foramen, and 
it passes forwards in a minute canal in the posterior wall of 
the middle ear. 

The Tympanic (Mastoid) Antrum lies in the posterior part 
of the petrous portion of the temporal bone. It varies some- 
what in size, but it always communicates with the epitympanic 
recess (attic) of the middle ear through a passage termed the 
aditus, which is placed in the upper part of the anterior wall of 
the antrum. In addition, it communicates, either directly or 
indirectly, with the air-cells of the mastoid process, and the 
whole system is lined by a prolongation of the muco-periosteum 
of the middle ear. 

The relations of the antrum are very similar to those of the 



206 THE ORGANS OF SPECIAL SENSE 

tympanic cavity. Its roof is formed by the tegmen tympani 
(p. 200) and its floor by the jugular fossa (p. 200). Anteriorly, 
it is related to the middle ear. Posteriorly, a thin plate of 
bone alone separates it from the transverse (lateral) sinus, as 
the vessel descends in its groove on the mastoid portion of the 
temporal bone (p. 114). In its medial ivall the lateral semi- 
circular canal is embedded, while the facial canal turns 
downwards in the medial wall of the aditus. Laterally, the 
antrum is related to the lateral surface of the skull immedi- 
ately behind the upper part of the external acoustic meatus. 
In the infant this wall is only about one-eighth of an inch 
thick ; by the sixth year, it has increased to a quarter of an 
inch, and, in adult life, it varies from a half to three-quarters 
of an inch in thickness. 

Suppurative disease in the tympanic (mastoid) antrum is a 
fertile source of intra-cranial abscess. When the infection 
spreads in an upward direction, the temporal lobe of the brain 
is involved, but it may spread backwards, causing thrombosis 
of the transverse (lateral) sinus. This vessel receives many 
tributaries from the cerebellum, and the infection may spread 
along them, ultimately giving rise to a cerebellar abscess. 
Spread in a medial direction involves the internal ear, and 
chronic progressive inflammation of the labyrinth (p. 90) is 
the result. 

The Internal Ear consists of a complicated, closed, mem- 
branous tube, termed the membranous labyrinth, which is 
situated in the osseous labyrinth, a large space in the interior 
of the petrous temporal. The anterior part of the osseous 
labyrinth is known as the bony cochlea, the middle part is 
termed the vestibule, while the posterior part constitutes the 
osseous semicircular canals. 

The anterior extremity of the membranous tube is spirally 
coiled to form the cochlea, and the posterior end of the cochlea 
opens into a small sac which is known as the saccule. The 
posterior extremity of the tube is arranged to form three semi- 
circular ducts, set, respectively, in vertical, frontal (coronal), 



THE EAR 



207 



and horizontal transverse planes. Both extremities of each 
semicircular canal open into a sac, termed the utricle (Fig. 80). 

The ductus endolymphaticus issues from the saccule and 
unites with the ductus utriculo-saccularis from the utricle. By 
means of these connections the endolymph circulates freely 
throughout the whole of the membranous labyrinth. 

The saccule, the utricle and their ducts are all placed in the 
vestibule of the osseous labyrinth. 

The membranous labyrinth does not occupy the whole of 
the available space within the osseous labyrinth, and the inter- 
val between it and the bone is filled with a fluid, termed peri- 




FlG. 80. — Diagram of the Membranous Labyrinth. (Turner's Anatomy.) 



DC. Ductus cochlearis. 
S. Saccule. 



SC. Semicircular ducts. 
U. Utricle. 



dr. Ductus reuniens. 
dr. Ductus vestibulL 



lymph. When the foot-piece of the stapes is moved medially, 
waves are set up in the perilymph, and they pass up the 
cochlea to its summit and then descend to impinge on the 
membrane which closes the fenestra cochleae (rotunda) 
(p. 204). As the waves pass along, they are transmitted 
through the wall of the membranous cochlea to the endo- 
lymph and so stimulate the processes of the cells which are 
connected with the terminal fibres of the cochlear division of 
the acoustic nerve. 

The terminal branches of the vestibular division of the 
acoustic nerve end in and around specialised cells in the walls 
of the membranous semicircular ducts. They are stimulated 
by movements in the endolymph, and they are also affected 



208 THE ORGANS OF SPECIAL SENSE 

by conditions which interfere with the tension of the labyrin- 
thine fluid. Meniere's disease (p. 90) may be caused by an 
increase in pressure, possibly owing to over-secretion of endo- 
lymph, or it may also be caused by haemorrhage into the 
interior of the semicircular ducts. Both ' of these factors 
produce their results by direct mechanical stimulation of the 
terminal branches of the vestibular nerve. 

The cochlea is the essential part of the auditory apparatus, 
while the semicircular ducts are concerned with equilibration. 

The Eve 

1. The Lacrimal Apparatus. — The Lacrimal Gland lies 
in contact with a depression in the antero-lateral part of the 
roof of the orbit. Inferiorly, it rests on the eyeball, behind, 
and on the superior fornix of the conjunctiva, in front, so that 
when the upper eyelid is everted, the outline of the anterior 
part of the gland can be made out. It is from the anterior 
part of the lacrimal gland that its numerous ducts pass, and 
they open directly into the conjunctival sac. The tears are 
carried downwards and medially across the anterior surface of 
the eyeball by the movements of the eyelids. The lacrimal 
secretion forms a thin film over the eyeball, and the surface 
tension of the fluid maintains the sheet intact. 

At the medial end of the border of each eyelid, there is a 
small papilla, in the centre of which a fine opening, termed the 
lacrimal function, leads into the lacrimal duct. These ducts 
carry away the excess of fluid from the medial corner of the 
conjunctival sac. At first, for about 2 mm., they are directed 
at right angles to the border of the lids, but they then turn, 
almost at right angles, and run medially to open into the 
lacrimal sac (Fig. 81). 

The Lacrimal Sac is placed in a groove in the anterior 
part of the medial wall of the orbit. Its upper extremity is 
blind, and, after being joined by the lacrimal ducts, the sac 
narrows inferiorly and becomes continuous with the naso- 



THE EYE 



209 



lacrimal duct. This duct lies in a bony canal in the lateral 
wall of the nose and opens below into the forepart of the 
inferior meatus of the nose, under cover of the anterior 
extremity of the inferior concha (turbinated bone). It is only 
half an inch long and is provided, near its lower end, with a 
small valve, which prevents the upward passage of air or fluids 
from the nose to the lacrimal sac. 
The secreto-moto/ 



nerves of the lacrimal gland are derived 




Fig. Si. — The Lacrimal Apparatus. (Turner's Anatomy.) 



1. Orbicularis oculi muscle. 
2, 3. Lacrimal canals. 
4. Lacrimal caruncle. 



5. Lacrimal sac. 

6. Nasolacrimal duct. 

7. Angular artery. 



from the lacrimal branch of the ophthalmic division of the 
trigeminal nerve, but they reach the semilunar (Gasserian) 
ganglion from the sympathetic plexus, which surrounds the 
internal carotid artery (p. 186). The lacrimal secretion is 
therefore diminished in paralysis of the ophthalmic nerve and 
in lesions which involve the cervical sympathetic trunk in any 
part of its course. 

It should be remembered that the gland does not begin to 
secrete until the second or third month, and that its secretion 

14 



210 THE ORGANS OF SPECIAL SENSE 

is partially or completely inhibited in toxic conditions. It will 
be found, therefore, that children who are seriously ill rarely 
shed tears. 

The puncta lacrimalia are normally in apposition with the 
ocular conjunctiva, and only under these conditions can the 
secretion enter the lacrimal ducts and so drain away through 
the lacrimal sac and naso-lacrimal duct into the nose. In 
paralysis of the orbicularis oculi (p. 82), the puncta fall away 
from the surface of the eye and the lacrimal secretion, being 
unable to enter the ducts, overflows on to the cheek, constitut- 
ing the condition of epiphora. The same condition will arise 
if the punctum is too narrow, either congenitally or following 
inflammatory conditions, or if there is any obstruction in the 
naso-lacrimal duct. 

2. The Eyelids. — The skin of the upper eyelid is supplied 
by the supra-trochlear, the supra-orbital and the lacrimal 
nerves (ophthalmic division of V.), while that of the lower eye- 
lid is supplied entirely by the infra-orbital branch of the 
maxillary division (p. 69). Under the skin lies the orbicularis 
oculi (palpebrarum) (p. 82) and, at the margins of the eyelids, 
the unstriated ciliary bundle is found. It derives its nerve- 
supply, not from the facial like the rest of the muscle, but 
from the sympathetic. Paralysis of these involuntary fibres 
gives rise to a variety of ptosis which has been termed pseudo- 
ptosis (p. 189). 

A plate of condensed fibrous tissue lies in each lid deep to 
the fibres of the orbicularis oculi. These are termed the 
superior and i?iferior tarsi, and the former is much the larger 
of the two. A thin ligamentous sheet extends from the 
margins of the bony orbital aperture to blend with the tarsi. 
Though not particularly strong, it is sufficient to influence the 
course of intra-orbital haemorrhage, which is guided downwards 
behind the conjunctiva (Fig. 82). 

The deep surfaces of both eyelids are covered by the con- 
junctival mucous membrane. From the muco-cutaneous 
junction the conjunctiva passes over the lid and it is then 



THE EYE 211 

reflected on to the anterior surface of the eyeball. The lines 
along which this reflection takes place are known as the 
fornices of the conjunctiva. Modified sweat glands open on 
the margins of the lids just behind the eyelashes. They may 
become obstructed and inflamed, giving rise to styes. The 
tarsal {Meibomian) glands, which are embedded in the tarsi, 
form thin reddish streaks, visible when the lid is everted. 
They open on the margin of the lid and are liable to become 
obstructed, causing tarsal cysts. 

3. The Eyeball consists of segments of two spheres, which 
differ in the size of their diameters, the anterior or corneal 
segment being much smaller and more sharply curved than the 
posterior or scleral segment. As a result, entering rays of light 
undergo a greater amount of refraction than they would if the 
eyeball were a perfect sphere. 

The ocular conjunctiva is thin and translucent, so that the 
white appearance of the fibrous sclerotic coat of the eyeball is 
rendered visible. It forms a very thin layer over the cornea. 
Subconjunctival hemorrhage may arise after rupture of the 
episcleral vessels, and it is then most profuse around the cir- 
cumference of the cornea ; or, it may be due to the spread of 
haemorrhage from the orbit (p. 210). In the latter case, the 
haemorrhage is most marked at the periphery of the conjunc- 
tiva and it is scanty in the neighbourhood of the cornea. 

The Sclera covers the posterior five-sixths of the eye. 
Anteriorly, it becomes continuous with the cornea, which 
covers the remaining sixth. The sclera is composed of strong 
fibrous tissue and it receives the insertions of the various 
ocular muscles (p. 57). It is pierced a little below and 
medial to its posterior pole by the optic nerve (p. 50), and 
around the point of entrance of the nerve it is pierced by the 
ciliary nerves and arteries. The anterior ciliary arteries run 
forwards on the outer surface of the sclera until they almost 
reach the corneo-scleral junction, and, before they pass through 
the sclera, they form anastomoses with one another. In this 
way an arterial ring is formed around the corneo-scleral 



2i2 THE ORGANS OF SPECIAL SENSE 

junction, but it is only visible when the vessels become 
engorged with blood, and is seen best in scleritis. 

The Cornea consists mainly of modified fibrous tissue, and 
it is directly continuous with the sclera. It is perfectly trans- 
lucent in order that light may pass through it to reach the 
retina, and it is therefore devoid of blood-vessels. Numerous 
lymph-spaces lie in the meshes of its fibrous tissue, and the 
cornea depends for its nutrition on the lymph which they con- 
tain. Ulcers of the cornea derive their blood-vessels from the 
anastomotic ring above referred to, and, after they heal, they 
are liable to produce small areas of opacity. 

The corneal lymph drains away into a circular canal, termed 
the sinus venosus sclera: {canal of Sc/ilemm), which lies in the 
corneo-scleral junction. This canal helps to drain away the 
aqueous humor from the anterior chamber of the eye (p. 216). 

The Chorioid is the vascular coat of the eye. It is placed 
within the sclera, to which it is attached by some pigment- 
containing connective tissue, but it does not extend quite so 
far forwards as the corneo-scleral junction. It contains the 
blood-vessels which supply the various coats of the eye, and it 
is separated from the retina internally by a translucent basal 
membrane. 

Congenital deficiencies may occur in the chorioid and are 
usually associated with similar deficiencies in the retina. The 
condition, which is known as coloboma, is commonly found in 
the lower and medial quadrant of the fundus. Owing to the 
absence of the retinal and chorioid coats, the sclera is seen 
over the affected area on ophthalmoscopic examination, and it 
appears as a clearly outlined patch, pearly-white in colour. 

Inflammation of the chorioid causes localised swellings, 
which lie deep to the retinal blood-vessels (p. 217), and can 
therefore be distinguished from inflammatory areas in the 
retina. The presence of chorioiditis in the region of the macula 
is of great importance, as the pressure and the inflammatory 
exudation usually give rise to permanent effects, and, on this 
account, the prognosis should always be very guarded. 



THE EYE 



21 



Anteriorly, the chorioid becomes continuous with the Ciliary 
Body and the Iris. The ciliary body consists of the ciliary 
muscle and the ciliary processes (Fig. 82). The ciliary 
muscle lies deep to the anterior part of the sclera and consists 




Fi<;. S2. — Antero-rosterior Median Section through the Eyeball. 



a. Upper eyelid. 

b. Lower eyelid. 

c. Fornix conjunctivae. 

d. Fascia bulbi (of Tenon). 
t'. Optic nerve. 

f. Superior rectus muscle. 

g. Inferior rectus muscle. 
h. Sclera. 



i. Cornea. 

j. Chorioid. 
k, I. Ciliary body. 

in. Iris. 

;/. Spaces of angle of iris 
(of Fontana). 

o. Retina. 
/, q. Hyaloid membrane. 



r. Hyaloid canal (of Still- 
ing). 

j-. Vitreous humor. 

;". Crystalline lens. 

11. Zonular spaces (canal 
of Petit). 

v. Anterior chamber. 

x. Posterior chamber. 



of meridional and circular fibres. The meridional fibres arise 
from the corneo-scleral junction and radiate backwards and 
inwards to the ciliary processes and the chorioid. When they 
contract, they draw the chorioid forwards and so relax the 
suspensory ligament of the lens (see Lens, p. 215). The 
circular fibres, which form a ring at the margin of the iris, act 



2i 4 THE ORGANS OF SPECIAL SENSE 

as antagonists of the meridional fibres. The ciliary processes 
project inwards behind the iris but in front of the crystalline 
lens. 

The Iris forms a contractile, perforated diaphragm, which 
is separated from the posterior aspect of the cornea by the 
anterior chamber of the eye. Its peripheral border is con- 
tinuous with the ciliary body and its free, central border 
bounds the pupil. The iris contains a number of unstriped 
muscle fibres. Some of these are arranged around the peri- 
phery and constitute the sphincter pupillce. They are supplied, 
through the ciliary ganglion, by the oculomotor nerve (p. 58) 
and their action serves to diminish the size of the pupil. 
Other fibres extend from the periphery towards the free, 
central margin, constituting the dilatator pupillce. They are 
supplied, through the ciliary ganglion, by the sympathetic 
fibres which enter the skull along the internal carotid artery 
(p. 186). The ultimate origin of these nerves is said to be in 
the oculo-motor nucleus. 

Inflammation of the iris is usually accompanied by severe 
pain, experienced, for the most part, over the area of distribu- 
tion of the ophthalmic nerve (Fig. 41). The inflammation 
may spread to the adjoining ciliary body and chorioid, but the 
most important complication arises from the formation of 
adhesions between the posterior surface of the iris and the 
anterior aspect of the crystalline lens. Such adhesions pre- 
vent the fluid in the posterior chamber of the eye from passing 
forwards into the anterior chamber (p. 216) and an increased 
intra-ocular tension results, constituting acute glaucoma. In 
order to prevent the occurrence of this complication, mydri- 
atics should be employed at an early stage and, provided that 
the measure is successful, should be continued until the con- 
dition is cured. 

The Retina forms the innermost coat of the eyeball. 
Its outer, pigmented layer is continued forwards over the 
ciliary processes on to the posterior aspect of the iris, but the 
nervous elements of the retina only extend as far forwards as 



THE EYE 215 

the ciliary body. At the point of entrance of the optic nerve, 
there are no nerve-cells in the retina, which is only represented 
by an incomplete layer, termed the lamina cribrosa (see 
Ophthalmoscopic Examination). 

The Vitreous Body, which occupies the posterior four- 
fifths of the eyeball, consists of the vitreous humor enclosed 
within a capsule, termed the hyaloid membrane. The Crystal- 
line Lens lies in a depression on the anterior aspect of the 
vitreous body, and it is connected to the hyaloid membrane 
by a suspensory ligament, which extends from the membrane 
beyond the periphery of the lens to the anterior aspect of the 
lens, where it blends with the capsule (Fig. 82). Circular in 
shape, the lens possesses a diameter of about 10 mm., while 
it is 4 mm. in thickness. It consists of concentric laminae of 
highly specialised fibrous tissue enclosed within an elastic 
capsule. When the eye is at rest, the anterior surface of the 
lens is not so convex as the posterior surface, but, when the 
meridional fibres of the ciliary muscle contract, the suspensory 
ligament, which is adherent to the ciliary processes, is drawn 
forwards and, owing to the elasticity of its substance, the lens 
becomes more convex on its anterior surface. As age advances, 
the tissue of the lens becomes denser and loses its elasticity, 
thus accounting for the condition of presbyopia. When the 
pupil of a presbyopic subject is examined obliquely in reflected 
light, the appearance is suggestive of cataract, but ophthalmo- 
scopic examination will be sufficient to show that the media 
are quite translucent. 

Congenita/ malposition of the crystalline lens is a rare 
abnormality and it is due to failure in development of the 
suspensory ligament. 

The normal lens is perfectly translucent and, therefore, can 
contain no blood-vessels. During the period of its formation, 
however, the lens is supplied with blood by a small branch of 
the ophthalmic artery, which passes forwards from the porus 
opticus (optic disc) in a small canal in the vitreous body. 
This artery disappears during the fifth month of intra-uterine 



2i6 THE ORGANS OF SPECIAL SENSE 

life, but, should it persist, it will give rise to one form of con- 
genital cataract. When the lens is in its proper position, its 
margins cannot be seen on ophthalmoscopic examination, 
even when the pupil is as widely dilated as possible. The 
observation of part of its margin shows that the lens is dis- 
located or partially dislocated. This injury involves complete 
or partial rupture of the suspensory ligament and, since it has 
lost its attachments, the lens trembles visibly when the eye is 
moved — iridodonesis. 

The Posterior chamber of the eye is the small space which 
intervenes between the peripheral part of the anterior surface 
of the lens and the posterior aspect of the iris. It contains a 
clear fluid, termed the aqueous humor, which is secreted by 
the ciliary processes. Through the opening of the pupil the 
aqueous humor of the posterior chamber communicates with 
that in the anterior chamber, but, if this communication is 
prevented by the formation of adhesions between the lens and 
the iris, the fluid in the posterior chamber accumulates and 
causes an increase in the intra ocular tension. 

The Anterior chamber of the eye is bounded in front by the 
cornea and behind by the anterior aspects of the iris and the 
central portion of the lens. In the angle between the peri- 
pheral margin of the iris and the cornea, the aqueous humor 
drains away into the sinus venosus scleras (canal of Schlemm) 
(p. 212), and, therefore, cases of glaucoma which are due to 
obstruction of the normal communication between the anterior 
and posterior chambers of the eye are readily cured by the 
performance of iridectomy. 

On Ophthalmoscopic Examination, the red reaction of 
the retina, which is caused by the great vascularity of the 
chorioid and the corresponding opacity of the sclera, is at 
once seen. The Porus Opticus {Optic Disc) can be found by 
observing on the cornea the image of the lamp, utilised in the 
examination. By manipulating his mirror, the observer can 
cause the image to pass along the horizontal diameter of the 
cornea, and, when the image reaches the junction of the middle 



THE EYE 217 

and lateral thirds, the porus opticus conies into view. It con- 
sists of an oval, whitish area with an elevated circumference, 
termed the papilla of the optic nerve, and a depressed centre, 
termed the excavatio papilloe. The arteria centralis retina 
appears about the centre of the porus opticus and breaks up, 
in a fairly regular manner, to supply the retina. Large 
temporal branches pass to the supero-lateral and infero-lateral 
quadrants, while corresponding branches are distributed to the 
nasal half of the field. Two smaller branches, the upper and 
lower macular arteries, pass laterally to the region of the 




Fir,. S3. — The Normal Fundus, showing the Porus Opticus (Optic Disc 
and the Retinal Blood-vessels. (From Sym's Diseases of the Eye.) 

macula lutea. These arteries have corresponding veins, and 
the latter stand out more clearly on ophthalmoscopic examina- 
tion owing to their greater lumina and thinner walls. The 
walls of the retinal veins consist only of a layer of endothelial 
cells and they are therefore liable to rupture following injury, 
giving rise to retinal haemorrhages. No well-marked anastom- 
oses occur between the various branches of the central 
artery, and they communicate with one another only through 
the capillary plexuses. On this account, while thrombosis of 
the main trunk causes complete blindness, thrombosis of any 
of the larger branches give rise to an area of scotoma. 



218 THE ORGANS OF SPECIAL SENSE 

The macula lutea is placed at the posterior pole of the eye. 
It contains a large number of the highly specialised ganglionic 
cells, since it is the area on which the entering light rays are 
focused. On this account, too, it is crossed by no blood- 
vessels, and it depends for its nutrition on transudation from 
the surrounding areas. It lies slightly above and to the lateral 
side of the porus opticus. 

When the porus opticus (optic disc) is being examined, it 
must be remembered that the condition of the media — the 
cornea, the aqueous humor, the crystalline lens and the 
vitreous body — may greatly affect the field examined. Thus, 
in astigmatism, the outline of the porus opticus is greatly dis- 
torted, but it is the cornea and not the porus which is at fault. 

Ophthalmoscopic Examination offers a means of examining 
not only the coats and media of the eyeball, but also the 
condition of the peripheral circulation and blood-vessels. 
Important information can be obtained by this means in cases 
of early arterio-sclerosis. The loss of elasticity in the arterial 
wall produces in the retina, as elsewhere, tortuosity of the 
arteries, and, if the veins are examined, it will be found that 
they are compressed at the points where they are crossed by 
the thickened arteries, with or without peripheral engorgement, 
depending on the degree of pressure. The veins are the more 
readily influenced on account of the thinness of their walls 
{vide supra). Later, the vascular obstruction and the pressure 
on the lymph-spaces which surround the veins cause oedema 
of the retina. 

The Nose is described on page 325. 



Ill 

THE DIGESTIVE SYSTEM 

The Teeth 

In man and most mammals the teeth which serve during 
the early years of life are deciduous and disappear before the 
onset of puberty. 

The Deciduous Teeth begin to erupt between the sixth and 
the ninth months, but their appearance may be considerably 
delayed in constitutional diseases, of which rickets is by far 
the most common. The teeth of the mandible usually appear 
slightly earlier than those of the maxilla, but corresponding 
teeth on the two sides should erupt at practically the same 
time. The first teeth to appear are the central incisors, and 
they are soon followed by the lateral incisors. The first 
molars erupt early in the second year, and the interval between 
the first molar and the lateral incisor is filled up by the 
eruption of the canine, about the eighteenth month. The 
appearance of the second molar at the end of the second or 
the beginning of the third year completes the deciduous set. 
As the teeth make their way through the mucous membrane 
of the gums, they may, by stimulation of the sensory branches 
of the trigeminal nerve, give rise to reflex disturbances, which 
vary from slight malaise to severe convulsive fits. 

The Permanent Teeth begin to erupt during the sixth 
year, and the first to appear is the first molar tooth, which 
comes to the surface of the gum behind the second deciduous 
molar. As a result of this arrangement, the child is able tQ 



220 THE DIGESTIVE SYSTEM 

masticate its food satisfactorily while the deciduous molars 
are being shed. The medial and lateral incisors appear 
during the seventh and eighth years respectively, and are 
followed by the first and second premolars, which erupt 
during the ninth and tenth years. The premolars cannot 
appear above the gum until the deciduous molars have been 
removed or have dropped out. The interval between the first 
premolar and the lateral incisor is filled by the canine, which 
has usually erupted by the end of the twelfth year. The 
second permanent molar varies somewhat in its time of ap- 
pearance, and it is not unusual for its eruption to be delayed 
till the fifteenth or sixteenth year. A similar variation is found 
in the date of eruption of the third molar tooth, which com- 
pletes the permanent set. It may appear at any time between 
the seventeenth and the thirtieth years. 

The roots of the molar and of the premolar teeth lie in 
relation to the floor of the maxillary sinus (antrum of High- 
more), and, when it is necessary to drain the sinus, access can 
be obtained by removing one of these teeth, preferably a 
premolar. 

Failure of a tooth to erupt is never caused by faiiure to 
develop. It may remain embedded in the bone or, if a 
maxillary tooth, it may be found in the hard palate. This 
condition may affect any of the teeth, but it is found most 
frequently in connexion with the third permanent molar. 
Such a misplaced tooth may give rise to very pronounced 
reflex symptoms, of which acute neuralgia in the area of dis- 
tribution of the fifth nerve is the most common. 

In cases where congenital syphilis is suspected, the condition 
of the teeth may offer valuable evidence. In congenital syphilis 
the incisors are short and peg-shaped, and their cutting edges 
are definitely notched,— Hutchinson's Teeth. The notching 
is not natural, for, on eruption, the teeth are normal in 
appearance. The adamant (enamel) is very thin and soon 
becomes broken off, leaving the dentine exposed and causing 
the characteristic notches. It is only when the upper central 



THE TEETH 



221 



incisors are affected in this way that a positive diagnosis of 
congenital syphilitic affection of the teeth may be made. 

Additional incisors and rudimentary fourth molars are 
occasionally met with, but they are of special interest only 
to the comparative anatomist. 




Fig. 84. — Radiogram of Anterior Portion of Head, showing non-eruption 
of the third upper molar tooth of the right side. The outline of the 
tooth can be seen embedded in the maxilla. (From a Radiograph 
by Chas. A. Clark, Esq., L.D.S.Eng.) 



The nerve-supply of the teeth is derived from the trigeminal 
nerve. The maxillary nerve supplies the teeth of the maxilla 
and the mandibular nerve those of the mandible. 

The lymph vessels of the maxillary teeth terminate in the 
submaxillary lymph glands, which are closely related to the 
submaxillary salivary gland; those from the molar teeth are 



222 THE DIGESTIVE SYSTEM 

also connected with the anterior auricular lymph glands, which 
lie superficial to the parotid. The lymph vessels of the mandi- 
bular teeth also join the submaxillary lymph glands, but some 
pass directly to the upper anterior group of the deep cervical 
glands. These glands are associated with the upper part of 
the internal jugular vein. 

The Salivary Glands 

The Parotid is the largest of the three chief salivary glands. 
It lies in a somewhat wedge-shaped recess, which is bounded 
posteriorly by the anterior border of the sterno-mastoid, 
anteriorly by the posterior border of the ramus and the 
condyle of the mandible, and superiorly by the floor of the 
external acoustic meatus. The anterior part of the gland 
passes forwards into the face, overlapping the masseter muscle, 
and is termed the facial process (Fig. 85). 

The parotid duct emerges from the facial process and, after 
passing forwards across the masseter, it turns medially to pierce 
the buccinator muscle. It then passes forwards for a short 
distance in the submucous tissue of the cheek and pierces the 
mucous membrane opposite the second molar tooth of the 
maxilla. Its orifice is sometimes marked by a small papilla, 
which may be felt with the tip of the tongue. The course of 
the duct corresponds, on the surface, to the middle third of 
a line drawn from the lower border of the external acoustic 
meatus to a point midway between the red margin of the 
upper lip and the ala of the nose. 

As the openings in the buccinator and in the mucous 
membrane through which the duct passes are not placed 
opposite one another, a valve-like arrangement is provided to 
prevent the backward passage of air or fluid. Despite this 
arrangement, the duct occasionally becomes greatly inflated 
and forms a distinct tumour in the cheek. The condition 
occurs most commonly in glass-blowers, who have to exercise 
considerable expulsive force in the performance of their craft. 



THE SALIVARY GLANDS 



223 



The parotid gland is surrounded by a strong sheath, con- 
tinuous with the deep cervical fascia, and, on this account, its 
enlargement in inflammatory conditions is somewhat restricted. 
The facial nerve, after emerging from the stylo-mastoid foramen 
(p. 80), enters the substance of the gland and breaks up into 
its terminal branches in that situation. It may occasionally be 
compressed in acute parotitis, owing to oedema of the gland 



Auriculo- Nerve to orbicularis 
temporal nerve oculi muscle 



Parotid gland — 



Great auricular 

nerve 

Sterno-mastoid 

muscle 




Orbicularis 
"" oculi muscle 




W- 




Masseter muscle 

— Buccinator mus. 

Anterior facial 

vein 



_ Submaxillary 
gland 



FIG. 85.— The Parotid ('.land and its Duct. 

within its unyielding sheath, and temporary facial paralysis 
may result. 

If the tip of the finger is placed in front of the tragus of the 
external ear, it will be found to sink into a depression when 
the mouth is opened. This depression is produced by the 
forward movement of the mandibular condyle and it contains 
a small part of the parotid gland, which may become enlarged 
in acute parotitis. Under these circumstances, the movements 
of opening and closing the mouth give rise to considerable 
pain, and are therefore very much restricted. 

Since the cartilaginous external acoustic meatus lies in a 



224 THE DIGESTIVE SYSTEM 

groove on the superior aspect of the parotid, it may be com- 
pressed when the gland is enlarged. This condition may give 
rise not only to painful symptoms but also to a slight degree 
of deafness. 

A small portion of the facial process is Occasionally quite 
separate from the rest of the gland. It lies immediately above 
the duct and is termed the accessory parotid (socia parotidis). 
In acute parotitis it forms a discrete little swelling in the 
cheek, and may then be mistaken for an inflamed lymph gland. 

The lymph vessels of the gland pass to the anterior auricular 
(p. 222) and the parotid lymph glands, and thence to the deep 
cervical lymph glands. 

The Submaxillary Salivary Gland lies under cover of 
the posterior part of the body of the mandible and is situated 
above the level of the hyoid bone. The main part of the 
gland is superficial and is in contact with the deep cervical 
fascia. Its duct passes forwards and upwards and opens 
through the mucous membrane of the floor of the mouth. 
Its orifice is placed on the summit of a small papilla, which 
is situated close to the frenulum of the tongue. 

The Sublingual Gland lies under cover of the anterior 
part of the body of the mandible and is more deeply placed 
than the submaxillary gland, since it is separated from the 
deep cervical fascia by the mylo-hyoid muscle (p. 72). Its 
superior border is in contact with the mucous membrane of 
the anterior part of the floor of the mouth and forms a slight 
bulge, which may be recognised with the tip of the tongue. 
The bulging is rendered more prominent if the finger is 
insinuated under the body of the mandible opposite the canine 
tooth and is thrust upwards. 

When the mouth is opened and the tip of the tongue is 
elevated, a fold of mucous membrane is seen in the lateral 
part of the floor of the mouth. This fold is termed the plica 
sublingualis and it indicates the position of the sublingual 
gland. It is pierced by the sublingual ducts, which vary in 
number from 8 to 20. 



THE MOUTH 225 

The salivary secretion contains an amylolytic enzyme, 
termed ptyalin, which is capable of acting on cooked starchy 
foods. At birth only the secretion of the parotid gland 
contains ptyalin, but, although the enzyme appears in the 
submaxillary and sublingual secretions during the third month, 
its amylolytic action is not completely developed until the end 
of the first year. The amylolytic action of the pancreatic 
secretion is similarly delayed, and hence it follows that but 
little starchy food should be given to children until they are 
a year old. 

Calcium salts are present in the saliva, more especially in 
the secretion of the submaxillary gland. The latter fact 
accounts for the deposition of tartar on the mandibular teeth 
and for the occurrence of submaxillary calculi. 

The nervous mechanism of the salivary secretion is referred 
to on page 189. 

The Mouth. — The mucous membrane of the cheeks, gums, 
lips and floor of the mouth is entirely supplied by the trigeminal 
nerve. Reference has already been made to the results of anaes- 
thesia of the cheeks and lips (p. 75) and to the similar results 
of paralysis of the buccinator (p. 84), which constitutes the 
chief muscular stratum of the cheek. 

The mucous membrane of the gums is firmly adherent to the 
periosteum, and consequently the accumulation of pus under 
the mucous membrane is associated with severe local pain. 

The lymph vessels of the gums do not all follow the same 
course. Those from the inner surface of the maxillary gums 
pass to the upper and anterior group of the deep cervical 
lymph glands (p. 222), while those from their outer surface 
terminate in the submaxillary lymph glands (p. 221). The 
lymph vessels from the anterior part of the outer surface of the 
mandibular gums follow the lymph vessels from the central 
part of the lower lip and end in the submental lymph glands, 
which lie on the mylo-hyoid muscles, immediately below the 
chin ; all the remaining lymph vessels from the mandibular 
gums join the submaxillary group. 
IS 



226 THE DIGESTIVE SYSTEM 

The Tongue consists of a muscular mass, partially covered 
by mucous membrane. Its anterior part lies almost horizontally 
in the floor of the mouth, while its posterior part lies almost 
vertically in the anterior wall of the oral part of the pharynx 
(Fig. 86). The junction of the anterior two-thirds with the 
posterior third of the tongue is marked in the median plane 
by a small depression, termed the foramen cactim, which 
possesses considerable morphological interest (p. 41 1 ). Immedi- 
ately in front of the foramen caecum, the vallate papillae are 
arranged in a V-shaped manner on the dorsum of the tongue. 

Collections of lymphoid tissue, termed the lingual tonsil, are 
situated under the mucous membrane of the pharyngeal portion 
of the tongue. They are of interest because they are very 
constantly enlarged in cases of status lymphaticus. 

The sensory nerve-supply of the tongue is derived from the 
lingual and the glossopharyngeal nerves (pp. 75 and 92), while 
the muscles of the tongue are supplied by the hypoglossal 
nerve (p. 107). 

The lymph vessels from the tip of the tongue join the 
submental glands (p. 225); those from the borders and sub- 
stance of the tongue pass to the submaxillary lymph glands 
(p. 221) and thence to the upper anterior group of the deep 
cervical glands ; those from the base of the tongue pass 
directly to the latter group. 

The Isthmus Faucium forms the communication between 
the mouth and the oral part of the pharynx. It is bounded, 
above, by the soft pa'ate : below, by the tongue : and, on 
each side, by the glosso-palatine arch (anterior pillar of the 
fauces), which extends from the lateral part of the lower 
surface of the soft palate to the side of the tongue. 

The Oral Part of the Pharynx lies behind the isthmus 
faucium. Above, it communicates freely with the naso- 
pharynx, but this communication is completely shut off when 
the soft palate is elevated. 

A fold of mucous membrane, termed the pharyngo-palatine 
arch (posterior pillar of the fauces), extends downwards on the 






THE MOUTH 



227 



lateral wall from the lateral extremity of the free posterior 
border of the soft palate. A triangular interval is enclosed 




Fig. 86. — The Interior of the Pharynx, viewed from behind, after 
removal of the posterior pharyngeal wall. 



1. Nasal septum. 

2. Inferior concha (turbinated bone). 

3. Soft palate. 

4. Uvula. 

5. Glosso-palatine arch (anterior pillar 

of fauces). 

6. Tonsil. 



7. Pharyngo-palatine arch (posterior 

pillar of fauces). 

8. Dorsum of tongue. 

9. Epiglottis. 

10. Ary-epiglottic fold. 

11. Upper aperture of larynx. 

12. Recessus piriformis. 



13. Posterior aspect of cricoid cartilage. 

between the pharyngo-palatine and the glosso-palatine arches 
(pillars of the fauces) and it contains the palatine tonsil, a 
structure of great importance during childhood. 



228 THE DIGESTIVE SYSTEM 

The palatine tonsil is formed by the outgrowth of numerous 
little diverticula from the pharyngeal wall. These diverticula 
become surrounded by a mass of lymphoid tissue, which 
rapidly increases in amount and bulges the mucous membrane 
inwards. An ill-defined capsule of fibrous tissue covers the 
tonsil on its lateral aspect. The original diverticula remain 
patent and form the tonsillar crypts, which become filled with 
a caseous exudate in follicular tonsillitis. The crypts of the 
tonsil provide access to many varieties of micro-organisms, of 
which the tubercle bacillus is much the commonest. During 
the early years of life, the lymphoid tissue of the palatine 
tonsils may hypertrophy to such an extent that they almost 
meet in the middle line, and this condition is usually accom- 
panied by a similar hypertrophy of the pharyngeal tonsil 
(p. 329). The respiratory difficulties caused by this enlarge- 
ment may be so great that the contour of the chest is greatly 
altered, pigeon-chest, Harrison's sulcus and other deformities 
being induced. 

The lymph vessels of the palatine tonsil pass to one of 
the upper deep cervical glands, placed in close relation with 
the internal jugular vein at the level of the greater cornu of fhe 
hyoid bone. From this lymph gland efferents pass to the lower 
group, some of which are intimately related to the cervical 
dome of the pleura. It has been suggested (p. 352) that 
tuberculous infection of the palatine tonsil may, through the 
medium of the lymph glands and vessels, be responsible for 
the production of apical phthisis. Other efferents descend 
into the thorax and establish connexions with the bronchial 
glands. In this way another route is opened up for the 
passage of tuberculous infection from the palatine tonsil to the 
lung. 

The posterior wall of the oral part of the pharynx is a 
common site of anglo-neurotic oedema, a circumstance which is 
accounted for by the laxity of the submucous tissue in this 
situation. 

The muscular wall of the pharynx is entirely deficient 



DEGLUTITION 229 

anteriorly, on account of the presence of the choanae 
(posterior nares), the isthmus faucium, and the laryngeal 
aperture (Fig. 86). It is formed posteriorly and on each side 
by the constrictor muscles, which become continuous below 
with the muscular coat of the cesophagus. These muscles 
play an important part in the act of deglutition, and they are 
assisted by the muscles of the tongue and soft palate. 

The act of deglutition comprises a voluntary and an in- 
voluntary stage, but the two overlap one another and are 
difficult to distinguish. The mouth is closed by certain of 
the muscles of mastication (p. 70), and the cheeks and 
lips are pressed against the teeth and gums by the con- 
traction of the buccinators and the orbicularis oris. The soft 
palate is raised and drawn tense so as to cut off the communi- 
cation between the nasal and the oral parts of the pharynx. 
The tongue and hyoid bone are suddenly drawn upwards by 
the mylo-hyoids, digastrics, etc., and the bolus of food is 
forced backwards through the isthmus faucium. As it enters 
the oral part of the pharynx, its passage is hastened by the 
approximation of the palatine arches (pillars of the fauces), 
which squeeze it onwards. The bolus is then acted on by 
the constrictors, which force it downwards into the cesophagus. 

Owing to the attachments of the thyreo-hyoid membrane 
(Fig. 121), the elevation of the hyoid bone is necessarily 
accompanied by elevation of the larynx, and, at the same 
time, the ary-epiglottic folds (p. 332) become shortened and 
approximated so that the apices of the arytenoids are brought 
into contact with the tubercle (cushion) of the epiglottis. In 
this way the cavity of the larynx is almost completely shut off 
from the pharynx. As a result, the breath is held during 
deglutition, and anything which may cause a sudden inspiration 
re-opens the communication so that a portion of the bolus 
may be drawn into the larynx. 

Not only does the act of deglutition demand a number of 
intimately related and complicated movements, but it also 
brings into action several different groups of muscles, which 



230 THE DIGESTIVE SYSTEM 

are innervated by different cerebral nerves. The fifth nerve 
is involved in closing the mouth ; the seventh, in compressing 
the lips and cheeks ; the ninth, in elevating the larynx ; the 
tenth and eleventh, in elevating the soft palate, in closing the 
larynx, in approximating the palatine arches-and in urging the 
bolus onwards to the oesophagus; the twelfth, in elevating the 
tongue. Paralysis of any one of the nerves involved causes 
an appreciable disturbance only when the lesion is bilateral, 
and the act of deglutition is interfered with most in lesions of 
the ninth, tenth and eleventh nerves (Bulbar Paralysis, p. 108). 

The (Esophagus is a muscular tube which begins in the 
neck at the level of the cricoid cartilage — sixth cervical 
vertebra — where it is continuous with the laryngeal part of 
the pharynx. It passes down through the thorax, pierces the 
diaphragm and terminates in the abdomen by becoming 
continuous with the stomach. 

In the neck, the oesophagus lies in front of the vertebral 
column, and, when it is obstructed or compressed against the 
bone in this region, swallowing becomes impossible, the food 
being rejected at once. Anteriorly, it is related to the trachea 
and the recurrent nerves (Fig. 50), while it is overlapped by 
the posterior borders of the lobes of the thyreoid gland. 
In the lower part of the neck, the thoracic duct is related to 
its left border. Enlargement of the thyreoid gland may cause 
dysphagia secondarily to dyspnoea (Fig. 50), but the condition 
is rarely met with in practice. 

In the thorax, the oesophagus continues its course down- 
wards in front of the vertebral column. In the upper part, it 
is placed behind the trachea and is crossed by the arch of the 
aorta (Fig. 113) and the left bronchus. In the lower part of the 
thorax, the oesophagus deviates slightly to the left and, as it 
passes through the diaphragm, it lies one inch from the median 
plane. As it descends, it lies behind the pericardial sac, and 
as a result of this relationship, swallowing causes pain in the 
presence of pericarditis (p. 289). 

The oesophageal opening is placed in the muscular part of 



THE CESOPHAGUS 231 

the diaphragm, and the fibres which surround it have a 
sphincteric action. 

In the abdomen, the oesophagus bends to the left to join the 
cardiac end of the stomach. This part of the tube is only half an 
inch in length, but, partly owing to the bend which it makes to 
the left and partly owing to the sphincteric action of the oeso- 
phageal opening in the diaphragm, it may hinder the operation 
of gastroscopy by obstructing the passage of the instrument. 

(Esophageal Obstruction. — The thoracic portion of the 
oesophagus may be compressed by aneurisms of the aortic 
arch (p. 319), by mediastinal tumours, originating either in 
the thymus or in the lymph glands, or by abscesses in con- 
nexion with the upper thoracic vertebras. Such abscesses 
cause obstruction by compressing the oesophagus against the 
unyielding aorta and left bronchus. 

Malignant stricture affects the oesophagus at the three points 
where it normally shows a slight degree of constriction. These 
occur — (1) At the commencement of the tube, or 6 inches 
from the incisor teeth ; (2) at the point where the oesophagus 
is crossed by the left bronchus, or 10 inches from the incisor 
teeth; and (3) at the distal end of the tube, or 15 inches 
from the incisor teeth. (Esophageal bougies should be 
graduated in such a way that the operator can locate the site 
of the stricture. Before such an instrument is passed, the 
possibility that the obstruction is due to an aneurism of the 
aortic arch must be carefully excluded. It should also be 
remembered that a carcinomatous stricture may be very friable, 
and it is then readily perforated by a bougie. A little difficulty is 
often experienced in guiding the instrument past the prominent 
upper border of the lamina (posterior arch) of the cricoid 
cartilage, and care must be taken not to diagnose a stricture 
at this point without sufficient evidence. 

In all muscular tubes the stage of hypertrophy on the 
proximal side of an obstruction is followed, sooner or later, by 
a stage of dilatation. On this account, when the site of an 
oesophageal obstruction is placed low down in the thorax, 



232 THE DIGESTIVE SYSTEM 

food is retained for some time before it is ejected, and there 
may be some doubt as to whether or not it has been within 
the stomach. The mucous membrane of the oesophagus 
contains numerous mucous glands, and, consequently, ejecta 
from the oesophagus are alkaline in reaction and are mixed 
with mucus. In all doubtful cases, the diagnosis can be made 
clear by examination with the fluorescent screen during the 
passage of a bismuth meal. 

In order to examine the oesophagus with X-rays, the patient is 
placed obliquely with reference to the screen, so that the shadow 
of the bismuth may be seen satisfactorily, as it passes down in 
front of the vertebral column and behind the pericardium. 

The arteries of the oesophagus are derived, in the neck, from 
the inferior thyreoids : in the thorax, from the descending 
thoracic aorta : in the abdomen, from the left gastric (coronary) 
artery. They anastomose freely with one another, and similar 
communications exist between the veins, which join the vena 
azygos in the thorax and the left gastric vein in the abdomen. 
In this way the systemic and portal circulations are connected 
with one another, and, in portal obstruction, this venous 
anastomosis may become greatly enlarged in the lax sub- 
mucous tissue of the oesophagus. The rupture of varicose 
veins in this situation gives rise to haematemesis, which may 
be the first sign of cirrhosis of the liver (p. 274). 

The nerves of the oesophagus are derived from both vagi, 
which form a plexus on its walls in the thorax (p. 100). This 
plexus is reinforced by fibres from the sympathetic trunks, and 
their centres in the spinal medulla are situated in the upper 
thoracic segments. Pain referred from the oesophagus is 
usually experienced over the lower part of the sternum, in 
the areas supplied by the terminal branches of the fourth 
and fifth intercostal nerves. It is most marked when violent 
peristaltic movements affect the circular muscular fibres on the 
proximal side of an obstruction. 



REGIONS OF THE ABDOMEN 



233 



Regions of the Abdomen. — Before the anatomy of the 
abdominal part of the alimentary canal is described, it is 
necessary to consider the plan adopted for the subdivision 
of the abdominal cavity into certain arbitrary regions. The 
following imaginary planes are utilised for the purpose. 

The subcostal plane passes horizontally through the body 
on a level with the most dependent parts of the tenth costal 
Posteriorly, it cuts the vertebral column near the 



cartilages. 




Fig. 87. — Anterior Aspect of Trunk, showing the planes utilised for 
the surface topography of the abdominal viscera. 



1. Transpyloric plane. 

2. Subcostal plane. 



3. Intertubercular plane. 

4. Right and left lateral planes. 



upper border of the third lumbar vertebra. The intertubercular 
plane, which is parallel to the subcostal plane, passes through 
the tubercles on the iliac crests and cuts the vertebral column 
near the upper border of the fifth lumbar vertebra. These two 
horizontal planes are intersected at right angles by two sagittal 
planes, which pass through the mid-points of the two clavicles ; 
they are known as the right and left lateral planes (Fig. 87). 
By these four planes the abdominal cavity is divided into 
nine regions, and the lines along which the planes cut the 
surface of the anterior abdominal wall may be utilised in 



234 THE DIGESTIVE SYSTEM 

referring the individual viscera to the surface of the body. 
The three regions which occupy the median plane are termed 
from above downwards, the epigastric, the umbilical and the 
hypogastric regions respectively. 

The transpyloric plane, though not utilised in the sub- 
division of the abdominal cavity, is extremely useful in con- 
nexion with the relations of viscera to the surface. It passes 
horizontally through the body and bisects the line which joins 
the upper border of the manubrium sterni to the pubic 
symphysis. As a rule, it cuts the vertebral column opposite 
the lower border of the first lumbar vertebra and lies about 
\\ inches above the subcostal plane. 

These regions and planes will be frequently referred to in 
the description of the various abdominal viscera. 

The Peritoneum 

The Peritoneum is the most extensive serous membrane in 
the body. In the male, it forms a completely closed sac, but, 
in the female, the peritoneal cavity communicates with the 
uterine (Fallopian) tube — and so indirectly with the exterior — 
through the ostium abdominale (p. 396). 

It is customary, as in the case of the pleura (p. 341), to 
refer to visceral and parietal layers, but it must be remembered 
that certain viscera, e.g. the pancreas, kidneys, etc., are retro- 
peritoneal, and that they are partially covered on their anterior 
surfaces by the peritoneum of the posterior abdominal wall. 
The arrangement of the peritoneum in relation to the abdominal 
viscera is best comprehended by the study of sagittal and 
transverse sections through the abdominal cavity. 

A sagittal section in the median plane passes, successively, 
through the liver, the stomach, the transverse colon and coils 
of the small intestine (Fig. 88), and, on the posterior abdominal 
wall, it passes through the pancreas and the third part of the 
duodenum. When the cut surface of such a section is 
examined (Fig. SS), it is found that the layer of peritoneum on 




Fig. 88. — Median Sagittal Section through the Abdomen, to show the 
arrangement of the Peritoneum. (Turner's Anatomy.) 



A. Liver. 
/■'. Stomach. 

C. Transverse colon. 

D. Pancreas. 

A'. Duodenum, third part. 

/•'. Jejunum. 

G. Rectum. 

//. Uterus. 

A". Cervix uteri. 

'£,. Vaginal part of cervix. 



M . Os uteri externum. 
N. Vagina. 

O. Bladder. 

/'. Urethra. 

Q. Clitoris. 

k. Diaphragm. 
i. I .esser omentum. 

2. t neater omentum, 

3. Transverse meso- 

colon. 



4. Mesentery. 

5. Indicates epiploic fora- 

men (of Winslow). 

6. Omental luirsa (lesser 

sac). 
6'. Great sac. 

7. Utero-rectal fossa. 

8. Utero-vesical fossa. 

9. Parietal layer of peri- 

toneum. 



236 



THE DIGESTIVE SYSTEM 



the deep surface of the anterior abdominal wall extends upwards 
on to the inferior surface of the diaphragm, from which it is 
reflected on to the liver. It covers the superior and anterior 
surfaces and it extends on the inferior surface as far back as 
the porta hepatis (transverse fissure of the liver). There it 
comes into contact with a layer of peritoneum which is passing 
forwards on the inferior surface of the liver, and the two layers 
descend in contact with one another to the lesser curvature of 







Fig. 89. — Diagram of the Stomach and the Lesser Omentum, to show the 
lines along which the stomach is cut in Fig. 90, A, and in Fig. 91, B. 

the stomach. This fold, which connects the stomach to the 
liver, is termed the lesser (gastro-hepatic) omentum, and, when 
it is examined on surface view (Fig. 89), it is found to possess 
a free border at its right extremity. 

The two layers of the lesser omentum enclose the stomach, 
constituting its serous coat, and then descend from the greater 
curvature to form the greater omentum, which varies consider- 
ably in its downward extent. Inferiorly, the two peritoneal 
layers are carried upwards again on a more posterior plane till 
they meet and enclose the transverse colon. From the colon 



THE PERITONEUM 237 

the two layers pass upwards and backwards to reach the 
anterior border of the pancreas, where they finally diverge 
from one another. 

In Fig. 88 the lower part of the greater omentum is seen to 
consist of four layers, but in the adult these layers are generally 
fused to one another, and the anterior two layers, as they pass 
in front of the transverse colon, are commonly adherent to the 
gut. The short upper part of the greater omentum which 
intervenes between the greater curvature of the stomach and 
the transverse colon is termed the gastro-colic ligament. 

The fold which attaches the transverse colon to the inferior 
border of the pancreas is known as the transverse mesocolon. 
Its upper layer ascends over the posterior abdominal wall and 
is ultimately reflected on to the liver. It subsequently forms 
the posterior layer of the lesser omentum. The lower layer 
of the transverse mesocolon descends from the pancreas, 
and, after plastering the duodenum against the posterior 
abdominal wall, it is drawn off the wall to form the mesentery, 
which suspends the coils of the jejunum and ileum within the 
peritoneal cavity. 

It will be seen from Fig. 88 that a part of the peritoneal 
cavity is shut off behind the stomach. This portion is termed 
the omental bursa (lesser sac) ; it forms a sac which is com- 
pletely closed except at one point, where it communicates with 
the rest of the peritoneal cavity (great sac). The communica- 
tion lies behind the right free border of the lesser omentum 
and is termed the epiploic foramen (of Winslow). 

Sagittal sections demonstrate the structures which constitute 
the anterior and posterior walls of the omental bursa. The 
anterior wall is formed, from above downwards, 'by the liver, 
the lesser omentum, the posterior surface of the stomach and 
the gastro-colic ligament. The posterior wall is formed, from 
below upwards, by the transverse colon, the transverse meso- 
colon, the anterior surface of the pancreas and the viscera on 
the posterior abdominal wall. 

The left and right lateral boundaries can only be studied in 



2 3 8 



THE DIGESTIVE SYSTEM 



transverse sections through the abdomen. In 



Fig. 



90 a 



transverse section has been made so as to pass through the 
epiploic foramen, and the level of this section is represented on 
the surface of the stomach in Fig. 89. The great sac becomes 
continuous with the omental bursa behind -the right free border 
of the lesser omentum, which therefore constitutes the anterior 
boundary of the epiploic foramen, and it may be observed 
that the bile dud, the hepatic artery and portal vein are placed 




Fig. 90. — Transverse Section through the Abdomen at the level of 
the epiploic foramen (of Winslow), to show the disposition of 
the peritoneum. 

In this section the stomach is cut along the line A (Fig. 8-j). 



I. Stomach. 

II. Epiploic foramen. 
IV. Right kidney. 

V. Left kidney. 
VI. Spleen. 



VII. Omental bursa (lesser 
sac). 

2. Lieno-renal ligament. 

3. Gastro - splenic liga- 

ment. 



4. Aorta. 

5. Hepatic artery. 

6. Portal vein. 

7. Inferior vena cava. 

8. Bile duct. 



between the two layers of the lesser omentum at its right 
border. The inferior vena cava, as it ascends through the 
abdomen, lies behind the peritoneum on the posterior wall of 
the epiploic foramen, which separates it from the portal vein 
at this level (Fig. 90). 

^"hen the two layers of peritoneum which enclose the 
stomach are traced to the left, they pass from the fundus to 
the spleen, forming the gastro-splenic ligament (Fig. 90), and 
the left layer of this fold is continued over the gastric, dia- 



THE PERITONEUM 



J 39 



phragmatic and renal surfaces of the spleen. From the spleen, 
the two layers are continued backwards to the anterior surface 
of the left kidney, where they finally diverge from one another. 
It will be seen that the omental bursa, which lies behind the 
stomach, is bounded on the left side by the gastro-splenic 
ligament, the hilus of the spleen and the lieno-renal ligament. 
If a section is made through the abdomen immediately 
below the epiploic foramen (Fig. 89, B), the omental bursa 




Fig. 91. — Transverse Section through the Abdomen, below the level 
of the epiploic foramen (of Winslow). 

The section cuts the stomach along the line R in Fig. 89. 

3. Airta. 

4. Gastro - duodenal 
artery. 

5. Inferior vena cava. 

6. Portal vein. 

7. Bile duct. 



I. Stomach. 
II. Pylorus. 
III. Duodenum. 
IV. Right kidney. 

V. Left kidney. 
VI. Spleen. 



VII. Omental bursa (lesser 
fac). 



Iiga- 



1. Gastro - splenic 

nient. 

2. Lieno-renal ligament. 



is seen as a completely closed sac. The peritoneum on the 
posterior surface of the stomach (Fig. 91) covers the posterior 
aspect of the pylorus and is continued for a short distance 
over the posterior surface of the first part of the duodenum. 
It then becomes reflected on to the posterior abdominal wall, 
and this reflection forms the upper part of the right lateral 
boundary of the omental bursa. When Figs. 90 and 91 are 
compared with one another, it will be found that the two layers 
of peritoneum which separate the inferior vena cava from the 



240 THE DIGESTIVE SYSTEM 

portal vein and bile-duct in Fig. 90 have disappeared in 
Fig. 91, so that these structures become much more intim- 
ately related to one another. 

The jejunum and ileum are suspended within the peritoneal 
cavity by the mesentery. This fold possesses an oblique 
attachment to the posterior abdominal wall, extending from 
the left side of the second lumbar vertebra, downwards and 
to the right, into the right iliac fossa, and it permits a wide 
range of movement to the gut. The blood-vessels, nerves and 
lymph vessels pass to and from the intestine between its two 
layers, and the mesenteric lymph glands occupy a similar posi- 
tion. When the glands are enlarged and tuberculous, they 
throw definite shadows in radiograms, and they can be recog- 
nised by the irregularity of their disposition and by the fact 
that their distribution is quite different in radiograms taken at 
different times. 

The peritoneal cavity shows a natural subdivision into 
smaller parts. The supra-colic compartment lies above and 
in front of the greater omentum, the stomach, the lesser 
omentum and the liver (Fig. 88), and it communicates with 
the omental bursa (lesser sac). The infra-colic compartment 
lies below and behind the greater omentum, the transverse 
colon and the transverse mesocolon, and it is further sub- 
divided into right and left parts by the mesentery. The 
pelvis constitutes the lowest compartment of the peritoneal 
cavity. These compartments are not completely separated 
from one another, but inflammatory conditions tend, as 
a rule, to be localised to the compartment in which they 
originate. 

The peritoneum is a large lymph-sac and it contains lymph 
which normally transudes from the abdominal blood-vessels. 
The parietal peritoneum possesses stomata, which serve to 
drain away the lymph, and these stomata are most numerous 
on the inferior aspect of the diaphragm. In cases of peri- 
tonitis, it is important therefore to prevent septic material 
from reaching the inferior aspect of the diaphragm, and this 



ASCITES 241 

may be effected by keeping the patient in the semi-sitting 
posture or by raising the head of the bed. 

When the transudation from the abdominal veins is exces- 
sive, the stomata are unable to carry away all the fluid, and the 
condition of ascites is brought about. It may result from any 
pathological state which retards the outflow of blood from the 
portal vein or from the inferior vena cava. Thus it may be 
due to cardiac lesions (p. 316), cirrhosis of the liver (p. 274), 
or abdominal tumours. 

When fluid is present in the peritoneal cavity, it obeys the 
law of gravitation, unless it is limited by adhesions. If the 
examination is conducted with the patient in the dorsal 
decubitus, it will be found that the lateral regions of the 
abdomen are dull to percussion, whereas the areas near the 
median plane are tympanitic. If, however, the patient turns 
over on to his right side, it will be found that the left lateral 
region has become tympanitic, whereas the dulness is confined 
to the right half of the body. This alteration is partly due to 
gravitation and partly to the fact that the hollow viscera float 
on the upper surface of the ascitic fluid. 

Paracentesis Abdominis. — This operation may be carried 
out by means of Southey's tubes or by means of a simple 
trochar and cannula. It is of great importance to ascertain 
that the patient's bladder is empty (p. 367) before paracentesis 
abdominis is performed. The patient is placed in a sitting or 
semi-sitting posture, because, in that position, the fluid to be 
drawn off is brought into contact with the lower part of the 
anterior abdominal wall and the intestines, which float on its 
upper surface, are removed from risk of injury. The upper limit 
of the fluid is determined by percussion and the trochar is 
inserted, after due attention to asepsis, through the linea alba 
into the dull area. The fluid should be allowed to drain away 
slowly and the alteration of the intra-abdominal pressure, 
caused by its removal, may be compensated for by the gradual 
tightening of an adjustable abdominal bandage. 

Nerve-supply of the Peritoneum. — For many years 
16 



242 THE DIGESTIVE SYSTEM 

clinicians have taught that, although the visceral peritoneum 
is insensitive to stimuli which produce painful impressions 
when applied to the skin, the parietal peritoneum is a highly 
sensitive membrane. Mackenzie believes that the parietal 
peritoneum is in no way different from the 'visceral layer, and 
that the pain which is apparently referable to the parietal 
peritoneum is in reality due to stimulation of the numer- 
ous sensory nerve-endings which abound in the extra-peri- 
toneal fat. 

Little is known with regard to the particular segments of 
the spinal medulla which innervate the peritoneum, but it is 
probable that they are identical with the segments which 
innervate the abdominal wall. Abnormal stimulation of the 
nerves supplying the peritoneum gives rise to both viscero- 
sensory and viscero motor reflexes (p. 192). This condition 
is well shown when stomach contents escape into the peritoneal 
cavity following the perforation of a gastric ulcer. Pain is 
referred to the whole of the anterior abdominal wall, and the 
muscles of the wall, which are innervated by the same nerves, 
become contracted and board-like. 

The Stomach 

The Stomach is situated chiefly in the left hypochondriac 
and the epigastric regions, but it also descends for a variable 
distance below the subcostal plane (p. 233). At its proximal 
end, or cardiac orifice, which lies immediately below the 
diaphragm, 1 inch to the left of the median plane, the stomach 
becomes continuous with the oesophagus; at its distal end or 
pylorus, which lies at a lower level and slightly to the right of 
the median plane, it becomes continuous with the duodenum. 
The stomach possesses anterior and posterior surfaces, which 
are separated from one another by two borders, termed the 
lesser and greater curvatures. To the left side of the cardiac 
orifice, the stomach bulges upwards into the left cupola of 
the diaphragm, and this dilatation is referred to as the fundus. 



THE STOMACH 243 

The pyloric canal, which leads to the pylorus, is the 
narrowest portion of the stomach. 

The a?iterior surface of the stomach lies in the posterior 
wall of the supra- colic compartment of the peritoneal cavity, 
and is therefore related to the great sac (Fig. 88). This 
area lies in contact with (1) the left lobe of the liver, (2) the 
left half of the diaphragm, and (3) the anterior abdominal 
wall. The hepatic area consists of a strip along the lesser 
curvature, while the diaphragmatic area consists of the fundus 
and adjoining portion. The diaphragm separates this part of 
the stomach from the apex of the heart, the base of the left 
lung and the pleura. Great distension of the stomach may 
act mechanically upon the heart, causing palpitation and 
cardiac irregularity, and, in debilitated bed-ridden patients, it 
may cause some collapse of the lower lobe of the left lung by 
direct pressure. 

It is impossible to state accurately the size of a normal 
stomach, since it is constantly undergoing changes of shape 
which depend upon its physiological condition at the time of 
examination. When the patient is lying on his back, the 
positions of the cardiac orifice and the pylorus can be 
determined with sufficient accuracy for practical purposes. 
The cardiac orifice is placed behind the seventh left costal 
cartilage, 1 inch from the sternum, while the pylorus is 
situated on the transpyloric plane (p. 234), about half an inch 
to the right of the median plane. A line joining the right 
side of the cardiac orifice to the upper border of the pylorus, 
drawn with a slight downward convexity, represents the lesser 
curvature (Fig. 92). The greater curvature begins at the left 
side of the cardiac orifice and passes upwards and to the 
left, reaching its highest point on the fifth rib. It then passes 
downwards and to the left as far as the anterior axillary line. 
The rest of the greater curvature passes to the right with a 
gentle downward convexity, and finally ascends rather sharply 
to join the lower border of the pylorus (Fig. 92). 

A tympanitic stomach note is obtained on percussion over 



244 



THE DIGESTIVE SYSTEM 



those parts of the stomach which lie in relation to the anterior 
abdominal wall and to the lower limit of the left pleural sac. 
Superiorly, the note becomes resonant to light percussion as soon 
as the lower border of the lung is reached. To the right side, 
the tympanitic gastric area is bounded by the liver dulness, 
and, to the left side, by the splenic dulness. Inferiorly, the 
greater curvature of the stomach is closely related to the trans- 




Fig. 92. — Anterior Aspect of the Trunk, showing the surface relations 
of the liver, the stomach and the large intestine. 

Note. — The reference lines are the same as those shown in Fig. 87. 



verse colon, which yields a tympanitic note of a somewhat 
different quality on percussion (PI. II.). 

The area on the costal parietes of the left side which yields 
a tympanitic gastric note to percussion under normal conditions 
is termed Traube's Space. From the description which has 
been given of the boundaries of this area, it will be clear that 
hepatic enlargement encroaches on the space from the right 
side, and that splenic enlargement encroaches on it from the 
left side. When the upper border of the space is found to be 
lower than normal, and formed by an area of absolute dulness, 
the condition is due to an effusion into the left pleural sac. 



THE STOMACH 



245 



The posterior surface of the stomach forms part of the 
anterior wall of the omental bursa ( Fig. 88), which intervenes 
between the viscus and its " bed." When an ulcer on this 
surface of the stomach becomes perforated, the omental bursa 




. 5 4 — "" ' Diaphragm 



Cardiac end 
of stomach 
Gastric sur- 
face of spleen 
Left supra- 
renal gland 
Left kidney 
Splenic 
vessels 



— 4- Pancreas 



Left kidney 

Left colic (splenic) 
flexure 



Commencement 
of jejunum 



Fig. 93. — The relations of the Left Kidney and the Viscera which 
form the " bed" of the Stomach. 



is infected. If the ulcer is situated near the pylorus, the 
epiploic foramen (of Winslow) may be closed by adhesions, 
and the infection is therefore prevented from spreading to the 
greater sac. The stomach-bed forms a shelving ledge over 
which the stomach may slip up or down, according to the 



246 THE DIGESTIVE SYSTEM 

position of the body. Above, it is formed by the gastric 
surface of the spleen, the anterior surfaces of the left kidney 
and supra-renal gland, and the posterior abdominal wall. 
Below, it is formed by the anterior surface of the pancreas, 
the transverse mesocolon and the transversa colon (Fig. 88). 
The stomach may become adherent to any of these viscera in 
the presence of a gastric ulcer, and death has been recorded 
in several cases from haemorrhage due to erosion of the 




Fig. 94. — Normal Tonic Stomach. Radiograph taken in upright 
position. ( From Knox's Radiography. ) 

splenic artery, which runs along the upper border of the 
pancreas (Fig. 93). 

Radiographic Examination of the Stomach. — The peritoneal 
folds which anchor it to the neighbouring viscera permit the 
stomach to alter its position under the action of gravity. This 
fact has been clearly demonstrated by the examination of the 
organ with X-rays, after the patient has been given a bismuth 
meal. Under examination with the fluorescent screen, the 
outline of the stomach is very indistinct when the patient is 



THE STOMACH 



247 



lying on his back, but it becomes quite evident when the 
vertical position is adopted. The stomach becomes tubular 
and assumes a J-shape. The long limb of the J is vertical 
and lies entirely to the left of the median plane, its lower limit 
often reaching the fibro-cartilage (intervertebral disc) between 
the fourth and fifth lumbar vertebrae. The short limb of the 
J passes upwards and to the right and terminates at the 
pylorus, which descends to the level of the second or third 




FlG. 95. —Atonic, dilated, Stomach. Radiograph taken in upright 
position. (From Knox's Radiography.) 

lumbar vertebra in the erect attitude. In a healthy stomach, 
in which the tonus of the muscular wall is good, it will be 
found that the upper level of the bismuth is maintained at a 
higher level in the long limb than it is in the short limb, and 
that the fundus, since it contains a certain amount of gas 
(Fig. 94), is outlined as a clear semicircular area on the top 
of the long limb. 

Marked variations from the typical description indicate the 
existence of pathological conditions. Thus, in radiograms 



248 THE DIGESTIVE SYSTEM 

taken with the patient in the erect posture, the presence of 
the pylorus at the level of the first lumbar vertebra indicates 
that it is prevented from descending by pathological adhesions, 
and suggests the possibility of ulceration in the pyloric region. 
It may be found that, although the stomach at first assumes 
a typical J-shape, after a time its shape becomes very indefinite, 
and, as the two limbs disappear, the bismuth which they 
contain descends to the same horizontal level (Fig. 95). 
This appearance indicates a loss of tone in the muscular wall 
of the stomach, for, although at first able to support a higher 
column of bismuth in the long limb of the J, the muscle tonus 
soon becomes fatigued and gives way. 

The Gastric Secretion is intended to act mainly on proteids. 
Its most important constituents are pepsin and hydrochloric 
acid, and it should be observed that pepsin can carry out its 
proteolytic action only in an acid medium. Consequently 
when pepsin is administered in gastric disorders, it should be 
combined with an acid solution. Some of the hydrochloric 
acid is required to neutralise the alkalinity of the saliva which 
is swallowed with the food, while some of it combines with the 
proteins of the food. As a result, the amount of free hydro- 
chloric acid is very small and is no real indication of the 
amount secreted. 

In addition, the gastric mucosa secretes an enzyme, termed 
rennin, which has a special curdling action on milk. It acts 
on the casein, which is the principal proteid in milk, and 
converts it into an insoluble solid. This solid substance is 
apparently more readily acted on by pepsin than the soluble 
casein. It may be pointed out that if the milk is lacking in 
lime salts the action of the enzyme is seriously interfered with. 

Lactic acid may be present in gastric contents, but it is a 
product of carbohydrate decomposition and is not secreted by 
the gastric mucosa. 

In children the hydrochloric acid is relatively less in amount 
than it is in the adult, and consequently the gastric juice is 
not so strongly germicidal. 



THE STOMACH 249 

The capacity of the stomach in the new-born is only ii oz. 
At three months, it has increased to 4^ oz., at six months to 
6 oz., while at the end of the first year it can retain 9 oz. 
Thereafter it goes on increasing gradually until, in the adult, 
the average capacity is about 40 oz. or 1 quart. 

The Lymph Vessels of the stomach pass, by several routes, 
to terminate in the cceliac lymph glands, which are closely 
related to the commencement of the abdominal aorta. Before 
reaching the cceliac glands, the gastric lymph vessels pass 
through subsidiary groups, including — (1) glands in relation to 
the pylorus, which also receive afferents from the liver; and 
(2) glands lying along the upper border of the pancreas, which 
also receive afferents from the spleen and the pancreas. 

In malignant disease of the stomach, secondary growths are 
frequently found in the liver. They also occur in the pancreas 
and, more rarely, in the spleen. Occasionally the lower group 
of the deep cervical glands of the left side may be affected. 
In this case the infection is carried by the thoracic duct 
(p. 324), which, at its lower end, receives the efferents from 
the cceliac lymph glands. 

Nerve-supply of the Stomach. — The stomach derives its 
nerve-supply from two sources, namely, — (a) the sympathetic 
and {b) the vagi. 

(a) At an early period of development the stomach is simply 
a localised dilatation of the primitive foregut, and, at this 
period, it receives its nerve-supply. The proximal or cardiac 
end of the tube, therefore, is supplied from a higher segment 
of the spinal medulla than the pyloric end. These nerves 
have their centres in the fifth, sixth, seventh and eighth 
thoracic segments, and they pass by the white rami com- 
municantes to the thoracic part of the sympathetic trunk. 
They descend in the greater splanchnic nerves (p. 187) to the 
cceliac ganglia and thence are carried on the coats of the 
gastric blood-vessels to the stomach. 

Viscero-sensory and viscero-motor reflexes (p. 192) occur 
with great frequency in pathological conditions of the stomach, 



250 THE DIGESTIVE SYSTEM 

and Mackenzie has pointed out that it may be possible to 
diagnose the site of a gastric ulcer from the position of the 
areas of cutaneous hyperalgesia, when such are present. 

Gastric referred pain is experienced in the skin areas sup- 
plied by the fi r th to the eighth thoracic nerves. As a rule 
the anterior terminal branches of the anterior rami (primary 
divisions) of these nerves are affected, and the pain is con- 
sequently referred to the epigastric region, but, at the 
same time, pain may be experienced over the wide areas of 
distribution of the lateral branches of the intercostal nerves 
of the left side. 

When a "focus of irritation" (p. 195) is established in 
the spinal medulla as the result of a gastric lesion, areas 
of cutaneous or muscular hyperalgesia may be found on 
careful examination. In most cases they occur over the 
upper part of the left rectus abdominis muscle, but they 
should also be sought for over the left sacro-spinalis (erector 
spinae). 

An area of cutaneous hyperalgesia, caused by an ulcer near 
the cardiac end of the stomach, will, theoretically, be situated 
in the region supplied by the fifth thoracic nerve. On the 
other hand, a similar area, caused by an ulcer near the pylorus, 
will be found in the region supplied by the eighth thoracic 
nerve (Fig. 96), i.e. the lower part of the epigastric region. 
Ulcers affecting the body of the stomach will give rise to areas 
of cutaneous hyperalgesia situated in the region supplied by 
the sixth and seventh thoracic nerves. 

Gastric lesions may give rise also to the viscero-motor reflex 
(p. 197), and, since the viscero-sensory reflex is usually 
limited to the areas supplied by the anterior terminal branches 
of the fifth to the eighth intercostal nerves, it is not surprising 
to find that the viscero-motor reflex is usually limited to the 
upper part of the left rectus abdominis, which is supplied by 
the same nerves. When the lateral branches of these nerves 
are affected, localised contractions may be found in the upper 
part of the external oblique muscle, and, when the posterior 



THE STOMACH 



251 



rami (primary divisions) are involved, similar areas may be 
found in the sacro-spinalis (erector spins). 

(b) The two vagus nerves enter the abdomen through the 
oesophageal opening in the diaphragm and break up to form 




f Photo by Alinari. 

Fig. 96. — The Nerve-supply of the Anterior Aspect of the Trunk. 

plexuses on both surfaces of the stomach. Some small twigs 
from these plexuses pass to the liver and the small intestine. 

Afferent impulses from the stomach may pass through the 
sympathetic to the spinal medulla or they may be carried by 
the vagi to the medulla oblongata. When a lesion of the 



252 THE DIGESTIVE SYSTEM 

stomach is present, a "focus of irritation" (p. 195) may be 
established in the medulla oblongata as well as in the spinal 
medulla. On the ingestion of food afferent impulses ascend to 
the medulla oblongata, and the resulting response probably 
governs the gastric peristalsis. If a "focus of irritation" is 
present in the medulla oblongata, these normal afferent stimuli 
become exaggerated as they ascend to the cortex and they 
cause an exaggerated response, e.g., emesis. It may be noted 
that such a focus may be caused by a lesion in any part of the 
stomach, and that, on this account, the rapidity with which 
emesis follows the ingestion of food merely indicates the 
presence of a "focus of irritation " and is no guide to the site 
of the lesion. 

Abnormal afferent impulses from the gastric branches of the 
vagus may " overflow " in the medulla oblongata and affect 
the neighbouring nerve-cells. This " overflow " stimulus may 
affect the cells which exert a depressor influence on the heart, 
and in this way, without any cardiac lesion, bradycardia may 
be associated with lesions of the stomach. Similarly, the 
irritable, uncontrollable cough which sometimes accompanies 
gastric disturbances is caused by the exaggeration of normal 
afferent impulses from the larynx, as they pass through a 
"focus of irritation " in the medulla oblongata. 

At the same time it must be remembered that, just as gastric 
lesions may give rise to disturbances in other viscera either by 
"overflow" of impulses in the medulla oblongata or by the 
establishment of a "focus of irritation" in the spinal medulla, 
so the stomach may be affected reflexly in lesions of other 
viscera innervated by the vagi. Thus, stimulation of the 
auricular branch of the vagus in the external acoustic meatus 
may give rise to symptoms of serious gastric disorder (p. 96) ; 
a severe fit of coughing may culminate in vomiting: affections 
of the biliary passages may lead to the vomiting of food as 
soon as it is ingested. In the latter case, however, it is doubt- 
ful whether we have to deal with a pure vagus reflex or 
with a sympathetic reflex. 



THE DUODENUM 253 

The Small Intestine 

The Duodenum begins at the pylorus on the right side of 
the body of the first lumbar vertebra and terminates at the 
duodeno-jejunal flexure on the left side of the second lumbar 
vertebra. Between these two points, it forms a C-shaped bend, 
which encloses the head of the pancreas. 

The first part of the duodenum passes backwards, upwards 
and to the right in relation to the gall-bladder and the inferior 
surface of the liver. It lies in front of the bile-duct, portal 
vein, inferior vena cava and gastro-duodenal artery, and, 
although its terminal portion is covered by peritoneum only 
anteriorly, its commencement is covered both anteriorly and 
posteriorly. This latter fact accounts for the descent of the 
pylorus when the erect attitude is adopted. In radiograms, 
after the bismuth meal has passed through the pyloric canal, 
the commencement of the duodenum throws a shadow, which 
lies immediately above the pylorus (Fig. 94). 

Duodenal ulcers are usually situated on the antero-lateral 
wall of the first part of the duodenum. A small area in this 
situation is very constantly supplied by a special branch from 
the hepatic artery, and it has been suggested that this vessel is 
an end-artery and that the area in question is therefore not so 
richly supplied with blood as the rest of the duodenum. An 
ulcer in the posterior wall of this part of the duodenum may 
cause death from haemorrhage by eroding the gastro-duodenal 
artery (Fig. 91). 

The second part of the duodenum runs downwards in front 
of the hilum of the right kidney and extends to the lower 
border of the third lumbar vertebra. A little below its middle 
it is crossed by the transverse colon, and so its upper part lies 
in the supra-colic compartment, while its lower part is on the 
posterior wall of the right infra-colic compartment. The 
second part of the duodenum receives the secretions of the 
liver and the pancreas (pp. 262 and 269). 

The third part of the duodenum passes to the left and, after 



254 



THE DIGESTIVE SYSTEM 



crossing the median plane, ascends till it reaches the left side of 
the body of the second lumbar vertebra, where it bends down- 
wards and forwards, forming the duodenojejunal flexure. It 




Fig. 97. — The relations of the Right Kidney, the Duodenum and 
the Head of the Pancreas. 

The stomach, the first part of the duodenum, the lesser and greater omenta, the 
liver and the large intestine have all been removed. 
2. Diaphragm. 

11. Psoas major muscle. 

12. Bile duct. 



13. Portal vein. 



14. Hepatic artery. 

15. Splenic vein. 

16. Superior mesenteric vein. 

17. Duodeno-jejunal flexure. 



THE DUODENUM 255 

crosses in front of the inferior vena cava and the abdominal 
aorta, and it is itself crossed anteriorly by the superior 
mesenteric vessels and the root of the mesentery. 

With the patient in the dorsal decubitus the duodenum 
may be mapped out on the surface with a tolerable amount 
of accuracy, for, since for the most part it is retro-peritoneal, 
its position undergoes little variation. From the pylorus 
(p. 243), the first part passes upwards and to the right for 
a distance of from i| to 2 inches. The second part descends 
medial to the right lateral plane to the level of the umbilicus. 
The third part passes to the left, below and parallel to the 
subcostal plane (p. 233), and, on the left side of the median 
plane, it ascends to the duodeno-jejunal flexure. The latter 
point lies h inch below the transpyloric plane (p. 234) and 
about 1 inch to the left of the median plane (Fig. 124). 

The nerves which supply the duodenum are carried on the 
walls of its arteries. These are derived from two sources, namely, 
the cceliac artery and the superior mesenteric, and the nerves 
which they convey belong partly to the group of sympathetic 
nerves which supplies the stomach and partly to the group 
which supplies the jejunum. The centres for these nerves in 
the spinal medulla lie in the lower thoracic region (T. 8 and 9) 
and overlap the centres for the stomach and the jejunum. 
On this account the referred pain which is experienced in 
duodenal nicer cannot be distinguished from the referred pain 
caused by a gastric ulcer in the pyloric region, and the pain 
initiated by violent peristaltic movements of the duodenum in 
chronic intestinal stasis (p. 257) is in every way similar to the 
pain experienced in violent peristalsis of the jejunum. 

Some of the terminal branches of the vagi assist the 
sympathetic nerves to supply the duodenum. 

The Jejunum and Ileum constitute the freely movable 
part of the small intestine, and they are attached to the 
posterior abdominal wall by a continuous dorsal mesentery, 
which begins above on the left side of the second lumbar 
vertebra and, extending downwards and to the right, ends 



256 THE DIGESTIVE SYSTEM 

below in the right iliac fossa. This mesentery contains the 
blood-vessels, nerves and lymph-vessels of the intestine and a 
large number of lymph glands. The latter commonly become 
enlarged in tabes niesenterica and throw recognisable shadows 
in radiograms. It is characteristic of the'm that they are 
irregularly placed and that, owing to the mobility of the 
mesentery, they occupy different positions in radiograms taken 
at different times. 

Taken together, the jejunum and ileum form a tube about 
20 feet in length, but the two parts are not clearly marked off 
from one another. In the jejunum, the mucous membrane 
is thrown into numerous transverse folds which are termed the 
plicae circulares (valvulse conniventes). They serve to in- 
crease the size of the absorptive area without unduly increasing 
the length of the intestine. The plica? circulares decrease in 
number in the lower part of the jejunum, and they are almost 
absent in the lower part of the ileum. 

In the ileum, collections of lymphoid tissue, termed the 
intestinal tonsils (Peyer's patches), form elongated oval areas 
in the mucous membrane. They are especially well marked 
in the terminal part of the ileum and in the caecum. In typhoid 
fever these areas are the site of small circular ulcers, the 
confluence of which may form a typical ovoid patch, corre- 
sponding in outline to the shape of the area. In tuberculous 
disease the intestinal tonsils may be the site of chronic 
ulceration. In this condition the ulcer tends to spread in 
the direction of the intestinal blood- and lymph-vessels, i.e. 
at right angles to the long axis of the gut, and when such 
an ulcer heals the accompanying cicatricial changes result in 
the formation of annular strictures. 

Under certain conditions (p. 277), the terminal portion of 
the ileum may become kinked in such a way as to cause 
serious obstruction to the passage of the intestinal contents. 
As a result of this obstruction, the small intestine becomes 
abnormally distended and the weight of the gut drags the 
duodeno-jejunal flexure, which is fixed in position, in a down- 



THE LIVER 257 

ward direction. A secondary kinking, therefore, is brought 
about at the termination of the duodenum, which, in turn, 
becomes abnormally distended and reacts on the stomach. 
The absorption of toxic material from the loaded bowel gives 
rise to serious symptoms, and the condition has been termed 
chronic intestinal stasis. 

When no obstruction is present in the small intestine, a 
bismuth meal should reach the caecum within five hours. 

The Lymph Vessels of the small intestine terminate in the 
mesenteric glands (p. 256), which send efferents to join the 
lymph glands associated with the abdominal aorta. 

The Nerve-supply of the Small Intestine is derived 
from sympathetic fibres which have their centres in the lower 
thoracic segments of the spinal medulla. In addition, the 
duodenum and the first coils of the jejunum probably receive 
some of the terminal branches of the vagi. 

Referred pain in connexion with the small intestine is 
usually experienced in the umbilical region (Fig. 96), but, 
owing to the great length of the gut, the presence of areas of 
cutaneous hyperalgesia is not of the same diagnostic value as 
it may be in gastric disturbances. 

The mucous membrane of the small intestine secretes the 
succus entericus, which takes an active part in the digestion 
of carbohydrates. It contains enzymes which convert di- 
saccharids into monosaccharids, rendering them ready to be 
absorbed by the blood-vessels in the wall of the gut. 

In addition, the succus entericus contains a substance, 
termed secretin, which normally stimulates the flow of the 
pancreatic secretion (p. 270). Further, the succus entericus 
affects proteid metabolism by converting the inactive 
trypsinogen of the pancreas into trypsin, which has a powerful 
proteolytic action. 

The Liver 

The Liver occupies practically the whole of the right hypo- 
chondriac region and the upper part of the epigastrium, and 

17 



258 THE DIGESTIVE SYSTEM 

in addition it encroaches to a slight extent upon the right 
lumbar and the left hypochondriac regions (Fig. 92). 

The superior surface of the liver is in relation to the 
inferior surface of the diaphragm, which separates it from the 
right lung and pleural sac, the pericardium, and, to a much 
lesser extent, from the left lung and pleural sac. Collections 
of fluid in the right pleural sac or in the pericardium, or 
enlargement of the right side of the heart (p. 297), may exert a 
downward pressure on the liver and cause it to project below 
the right costal margin for some distance. 

A similar downward displacement of the liver may be caused 
by an intra-peritoneal subphrenic abscess, situated in the recess 
of the greater peritoneal sac which extends upwards and back- 
wards between the upper surface of the liver and the inferior 
surface of the diaphragm (Fig. 88). When the right lobe of 
the liver is the site of a tropical abscess, this peritoneal recess 
may become obliterated by adhesions. As a result, if the 
abscess burrows through the upper surface of the liver, it will, 
in time, perforate the diaphragm and burst into the right pleural 
sac or even into the lung itself. The latter complication can 
only occur when the lung is adherent to the diaphragmatic 
pleura, and the abscess is then evacuated by coughing. 

The anterior surface of the liver is roughly triangular in 
outline, the apex being directed to the left and the base to the 
right. The sharp lower margin of the liver, which forms the 
. inferior boundary of this surface, ascends obliquely as it passes 
from right to left (PI. II.). In the subcostal angle, the anterior 
surface of the liver is in direct contact with the deep surface of 
the anterior abdominal wall, and it can therefore be examined 
in this situation both by percussion and by palpation. 

On the right side, the anterior surface lies under cover of 
the costal margin. In its upper part it is overlapped by the 
pleural sac, and it is only in its lower part that it can be 
approached without meeting with the pleura. On the left 
side, the inferior border of the liver forms the right boundary 
of Traube's space (p. 244). 



THE LIVER 259 

Surface Marking of the Liver. — When the outline of 
the liver is determined by percussion on the anterior aspect 
of the body, it is the anterior surface of the viscus which is 
mapped out. Under normal conditions, with the patient in 
the dorsal decubitus, the upper limit of the liver dulness 
extends upwards into the fourth intercostal space on the right 
side, but, owing to the thickness of the lung which intervenes 
between the liver and the chest wall, it is not always easy to 
determine the upper border with accuracy. Where the upper 
surface of the liver is in relation to the heart, the limits of 
the viscus cannot be determined by percussion. 

During quiet respiration, the upper border of the anterior 
surface of the liver corresponds to a line drawn from a point 
half an inch below and medial to the right nipple to a point 
1 inch below and medial to the left nipple. This line passes 
through the xiphi-sternal junction and shows a slight downward 
convexity, which corresponds to the lower border of the heart. 

The inferior border of the liver can easily be determined by 
light percussion, which should be begun at some distance 
below the costal margin. On the right side, the inferior 
border coincides with the costal margin or projects a little 
beyond it in the right lateral line, and, as it is traced to the 
left, it ascends so as to cut the transpyloric plane in the median 
plane. It then passes upwards more sharply, and crosses the 
left costal margin opposite the tip of the eighth costal 
cartilage (Stiles). 

In rare cases, a part of the right lobe of the liver, lateral to 
the gall-bladder (p. 261), projects downwards, sometimes as far 
as the iliac crest. It is termed Reidel's lobe. The condition 
is congenital and has no pathological bearing. Consequently, 
care must be taken to avoid mistaking it for an abdominal 
tumour. A similar downward projection may, very occasion- 
ally, be found in connexion with the left lobe of the liver. 

In infants, the inferior border of the liver usually lies at 
least half an inch below the costal margin in the right lateral 
plane. This difference is accounted for partly by the greater 



2 6o THE DIGESTIVE SYSTEM 

relative size of the viscus (p. 304) and partly by the fact that 
the ribs are more nearly horizontal. 

The right lateral surface of the liver lies opposite the 
seventh, eighth, ninth, tenth and eleventh ribs in the mid- 
axillary line, and it is separated from them by the lower limit 
of the pleural sac and the diaphragm. Hepatic dulness can 
be obtained as high as the sixth intercostal space in the mid- 
axillary line, but in the sixth and seventh spaces it is masked 
by the resonant note of the lung, which intervenes between the 
upper part of this aspect of the liver and the chest wall. In 
the lower spaces, where the viscus is separated from the 
parietes only by the diaphragm and pleura, light percussion is 
sufficient to bring out the dull liver note. 

The posterior surface of the liver is in contact with the 
upper part of the posterior abdominal wall, from which it is 
separated by the oesophagus, on the left side, and the inferior 
vena cava, on the right side. Little can be learnt from per- 
cussion with reference to the extent of this surface, because, 
to the right side of the median plane, the hepatic dulness 
merges into the dull note produced by the right kidney 
(PI. III.). 

The lowest part of the descending thoracic aorta is only 
separated from the liver by the lower and posterior part of the 
diaphragm, and its pulsations may be transmitted to the 
anterior abdominal wall when the left portion of the liver is 
the site of new growth. 

The inferior surface of the liver is very oblique and looks 
downwards, backwards and to the left. On this surface the 
obliterated umbilical vein (ligamentum teres) lies in a cleft 
which serves to separate the liver into right and left lobes 
(PI. I.). This subdivision, however, is purely superficial, and 
the two lobes are directly continuous with one another. 

The inferior surface of the left lobe is related to the anterior 
surface of the stomach, which it overlaps in the neighbourhood 
of the lesser curvature when the body is in the supine posi- 
tion. The inferior surface of the right lobe is related, in its 




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THE LIVER 261 

posterior part, to the right kidney, and, in its anterior part, to 
the right (hepatic) flexure of the colon. Cases have been 
recorded in which a tropical abscess has ruptured into the 
right colic flexure and has been discharged per anum. 

The porta hepatis (transverse fissure of the liver) is placed 
on the inferior surface, and through it the hepatic artery and 
portal vein enter and the hepatic ducts leave the liver (PI. I.). 

The hepatic veins, which join the inferior vena cava just 
before it pierces the diaphragm, return the blood distributed 
not only by the hepatic artery but also by the portal vein. 
Sudden dilatation of the right atrium of the heart dams back 
the blood in the inferior vena cava, and this backward pressure 
is at once communicated to the hepatic veins, causing acute 
venous congestion of the liver. In this condition, the size of the 
anterior surface of the liver is much increased, and the skin 
and muscles of the upper part of the anterior abdominal wall 
may be acutely sensitive to ordinary tactile stimuli {vide infra). 
The enlarged liver exhibits pulsations which are identical with 
the pulsations of the internal jugular vein, as they are brought 
about in precisely the same way (p. 311). When the dilatation 
of the right atrium of the heart is more gradual in its onset, 
chronic venous congestion of the liver is brought about and may 
cause the viscus to project for a considerable distance below 
the costal margin. 

The Lymph Vessels of the liver are very numerous. Some 
pass to the cceliac glands directly, or through the subpyloric 
glands (p. 249). Others pierce the diaphragm and join the 
lymph glands in the mediastinal space. Secondary growths, 
therefore, may be found in the mediastinal glands in primary 
cancer of the liver. 

The Gall-bladder forms a small reservoir for the bile 
secreted by the liver. It occupies a fossa on the inferior 
surface of the right lobe of the liver, to which it is connected 
by its peritoneal covering. Its blind extremity or fundus pro- 
jects from under cover of the inferior border of the liver and 
comes into contact with the anterior abdominal wall, just 



262 THE DIGESTIVE SYSTEM 

medial to the tip of the ninth costal cartilage of the right side. 
The fundus can be mapped out on the surface in the angle 
between the right costal margin and the linea semilunaris, which 
corresponds to the lateral border of the rectus abdominis muscle. 

Inferiorly, the gall-bladder is in contact with the duodenum 
and the commencement of the transverse colon, and it may 
become adherent to the latter after attacks of cholecystitis. 
Under these circumstances, gall-stones may rupture into the 
colon and be discharged by the bowel (PI. II.). 

The neck of the gall-bladder narrows to form the cystic 
duct, which enters the porta hepatis and unites with the 
hepatic duct to form the bile duct. The mucous membrane 
which lines the cystic duct is redundant and projects into the 
lumen in the form of oblique folds. These folds may help to 
prevent the passage of gall-stones from the gall-bladder into 
the bile duct. 

The Bile Duct is formed by the union of the cystic with 
the common hepatic duct at the porta hepatis. It descends 
from the liver in the right free margin of the lesser omentum, 
where it lies in front of the portal vein (Fig. 90). It then 
passes behind the first part of the duodenum and, at the 
upper border of the head of the pancreas, it diverges from the 
portal vein, running downwards and laterally behind the 
head of the pancreas to terminate in the second part of the 
duodenum (Fig. 97). 

In the first, or supra-duodenal, part of its course the bile duct 
may be compressed by tumours of the liver or by enlarged 
lymph glands in the porta hepatis. As the duct is closely 
related to the portal vein in this situation, pressure which 
affects the duct is almost certain to affect the vein as well. 

In the retro-duodenal part of its course, the duct may be 
obstructed by tumours of the pylorus, which also affect the 
portal vein. In the terminal part of its course, the duct is not 
so closely related to the vein, and tumours of the head of the 
pancreas or chronic pancreatitis are less likely to exert pres- 
sure on the vein. They commonly compress the duct 



THE BILE DUCT 



263 



(p. 264) and they may also tend to obstruct the inferior vena 
cava, which lies behind it. 

At its lower end the bile duct pierces the muscular wall of 
the duodenum very obliquely and opens into a small space, 
termed the ampulla of Vater (Fig. 98), which lies in the 
submucous tissue. The main duct of the pancreas (p. 269) 




~--7 



Fig. 98. — Diagram of the Bile Duct and the Pancreatic Ducts, 
showing how they open into the Duodenum. 



Gall bladder. 
Right hepatic duct. 
Bile duct. 
Wall of duodenum. 



5. Ampulla of Vater. 

6. Accessory pancreatic duct. 

7. Pancreatic duct. 

8. Communication between 6 and 7. 



also opens into the ampulla, which possesses a single small 
opening into the interior of the duodenum. Owing to the 
obliquity with which the duct pierces the duodenal wall, gall- 
stones may become impacted before they reach the ampulla of 
Vater. In this case they are not so likely to obstruct the 
pancreatic duct, but they may do so if they succeed in entering 
the ampulla and are unable to pass through the small orifice 
into the duodenum. 



264 THE DIGESTIVE SYSTEM 

Obstruction of the bile duct is followed by the absorption 
of bile pigments into the blood, and they are deposited in 
many of the tissues of the body and under the skin and 
mucous membranes. When jaundice results from impaction of 
a gall-stone in the bile duct or from inflammation of the mucous 
membrane which lines the duct, its onset is sudden, and it is 
not, as a rule, accompanied by any signs of obstruction to the 
portal vein or the inferior vena cava. On the other hand, 
when jaundice results from pressure due to extrinsic causes, 
the condition is slow in its onset, increases steadily in degree 
and is frequently associated with signs of venous obstruction. 

Development of the Liver and Biliary Passages. — At 
a time when the stomach is scarcely discernible as a dilatation 
on the primitive fore-gut (p. 249), the liver arises as a hollow 
diverticulum from the ventral aspect of the gut immediately 
caudal to the pylorus. This bud soon bifurcates into two 
parts, one of which persists as a blind hollow sac and forms 
the gall-bladder. The cells which line the other proliferate so 
quickly that its lumen becomes obliterated and the solid mass 
of cells invades the surrounding mesoderm, which forms the 
fibrous framework of the liver. 

The Nerves of the Liver and Bile Passages. — Owing 
to the proximity of the point of origin of the liver to the 
stomach, it is not surprising to find that the sympathetic 
nerves which supply the liver and bile passages arise from 
segments of the spinal medulla (T. 7-9) in close relation to 
the segments which supply the stomach (T. 5-8). In addition, 
the liver receives branches from both vagi and a few twigs 
from the right phrenic nerve which descend along the inferior 
vena cava. 

It is well recognised that advanced pathological processes 
may occur in the liver and yet give rise to no painful 
symptoms. In this way, the liver closely resembles the lungs, 
kidneys and pancreas, and it has already been pointed out 
that these viscera contain very few unstriped muscle fibres 
In solitary tropical abscess of the liver, the patient often 



BILIARY COLIC 265 

complains of pain over the right shoulder. In this case, 
the abnormal afferent stimuli reach the fourth cervical 
segment of the spinal medulla by the phrenic nerve (p. 128), 
and " overflow " to the cells which are accustomed to receive 
stimuli from the posterior supra-clavicular (supra-acromial) 
nerves. As a result of this overflow stimulus, the patient 
experiences pain in the skin of the shoulder. It seems 
doubtful whether the phrenic nerve is affected in the liver 
itself, and it is more probable that it is involved by inflammatory 
thickening of the diaphragmatic pleura of the right side. 

The gall-bladder and the biliary passages, however, are pro- 
vided with muscular walls, composed of unstriped muscle 
fibres, and they can give rise to severe pain which is best 
exemplified during an attack of biliary colic. The passage 
or the attempted passage of a gall-stone along the bile 
duct is accompanied by excessive peristalsis of the muscular 
wall of the duct. As in the case of the alimentary canal, this 
peristalsis results in the production of acute pain. 

Referred pain in connexion with the gall-bladder or bile 
duct is experienced over the distribution of the peripheral 
branches of the seventh, eighth and ninth intercostal nerves, 
usually of the right side only (Fig. 96). In most cases it is 
restricted to the anterior terminal branches, but it may spread 
to involve the lateral branches or even the posterior rami 
(primary divisions). The pain, therefore, is felt over an area 
which is very similar to that affected in gastric disturbances, 
but, in the case of the biliary passages, it tends to radiate to 
the right side of the median plane. 

Pathological conditions of the gall-bladder or bile duct may 
also excite a viscero-motor reflex (p. 197), which shows itself 
as a localised contraction of the right rectus abdominis in its 
upper part, i.e. that part of the muscle which is innervated 
by the seventh, eighth and ninth intercostal nerves. 

The constant "overflow" of the abnormal afferent impulses 
from the biliary passages during an attack of biliary colic may 
establish a " focus of irritation " (p. 195) in the spinal medulla 



266 THE DIGESTIVE SYSTEM 

at the level of the seventh, eighth and ninth thoracic seg- 
ments. The excitability of the cells in these segments is 
temporarily increased, and this condition may manifest itself by 
the presence of areas of cutaneous hyperalgesia (p. 195) in the 
lower part of the right half of the epigastric region. Some of 
the nerve-cells connected with the stomach (p. 249) are 
situated in these segments and consequently, although the 
gastric mucous membrane may be perfectly healthy, the 
ingestion of food may give rise to referred pain, since the 
afferent impulses become exaggerated as they pass through 
the " focus of irritation." 

The bile duct also receives some of the terminal branches 
of the vagus, and, on this account, a " focus of irritation " may 
be established in the medulla oblongata following an attack of 
biliary colic. It seems probable that some such condition is 
responsible for the occurrence of vomiting at the end of an 
attack of biliary colic or following the ingestion of food after 
the cessation of the pain. 

It should be remembered that similar reflexes, though of a 
less pronounced type, may accompany inflammation or other 
pathological conditions of the gall-bladder or bile duct. Owing 
to the propinquity of the gastric and the hepatic centres in 
the spinal medulla, the symptoms produced by cholecystitis 
may be misinterpreted and they may be erroneously ascribed 
to some non-existent gastric disorder. For the same reason, 
the symptoms produced by gastric disturbances may be errone- 
ously ascribed to the gall-bladder, and the diagnosis may only 
be corrected at a subsequent operation. 

The Pancreas 

The Pancreas is an elongated gland which lies obliquely 
across the upper part of the posterior abdominal wall. With the 
exception of its tail, which is situated between the two layers of 
the lieno-renal ligament (p. 239), the pancreas is entirely retro- 
peritoneal, and it is therefore practically fixed in position. 



THE PANCREAS 



267 




''7 



FlG. 99. — The relations of the Right Kidney, the Duodenum and 
the Head of the Pancreas. 

The stomach, the first part of the duodenum, the lesser and greater omenta, the 
liver and the large intestine have all been removed. 



1. Supra-renal area. 

2. Diaphragm. 

3. Hepatic area. 

4. Duodenal area. 

5. T. 12 (subcostal nerve). 

6. Colic area. 

7. Iliohypogastric nerve 

8. Ilioinguinal nerve. 

9. Transversus muscle. 



10. Quadratus lumborum muscle, 
n. Psoas major muscle. 

12. Bile duct. 

13. Portal vein. 

14. Hepatic artery. 

15. Splenic \ ein. 

16. Superior mesenteric vein. 

17. Duodenojejunal flexure. 



268 THE DIGESTIVE SYSTEM 

The head of the pancreas lies in the C-shaped bend of the 
duodenum and consequently extends to the right of the median 
plane. Its anterior surface is related to the transverse colon 
(p. 280) and to the origin and first part of the portal vein. 
Posteriorly, the head of the pancreas is in relation to the 
inferior vena cava and to the bile duct, which descends 
obliquely behind its upper part (Fig. 99). 

This portion of the gland may be the seat of malignant 
disease and the symptoms produced are, for the most 
part, referable to the relations which have been enumerated. 
The bile duct lies in a deep groove in the head of the 
pancreas and it is very liable to be compressed, giving rise to 
jaundice which is gradual in its onset but which steadily 
increases in intensity. The inferior vena cava may be com- 
pressed, leading to cedema of the lower limbs, ascites, etc., 
and the circulation through the portal vein may be interfered 
with (p. 274). 

The neck and body of the pancreas extend to the left in front 
of the abdominal aorta. The body is somewhat triangular on 
section, possessing anterior, posterior and inferior surfaces, 
separated from one another by corresponding borders. The 
anterior border gives attachment to the transverse mesocolon, 
so that the anterior surface lies in the posterior wall of the 
omental bursa, where it takes part in the formation of the 
stomach-bed (p. 245), while the inferior surface looks down- 
wards into the infra-colic compartments. 

Tumours in connexion with the body of the pancreas may, 
when they are of large size, be palpated through the anterior 
abdominal wall, and they not uncommonly transmit the pulsa- 
tions of the abdominal aorta. Pancreatic cysts usually enlarge 
on the anterior surface of the gland, so that they project into 
the omental bursa. If they grow in an upward direction, they 
may thrust the lesser omentum before them and reach the 
anterior abdominal wall above the lesser curvature of the 
stomach, which is displaced downwards and to the left. In 
this case, percussion indicates an increase in the liver dulness, 



THE PANCREAS 269 

but, as the cyst is only covered by the muscular abdominal 
wall, careful palpation may determine that it is separate from 
the liver. In most cases, the cyst reaches the anterior 
abdominal wall below the greater curvature of the stomach, 
pushing the gastrocolic ligament in front of it. Percussion 
reveals the presence of a dull area which intervenes between 
the tympanitic stomach note above and the tympanitic note 
of the transverse colon below. 

The main duct of the pancreas begins in the tail of the 
gland and passes to the right ; after traversing the body and 
head of the pancreas the duct pierces the duodenal wall and 
opens into the ampulla of Vater (p. 263). Near its termina- 
tion it may be obstructed by tumours of the head of the 
gland or by a calculus impacted in the ampulla of Vater. 
The latter condition is of two-fold interest. In the first 
place, it may be the forerunner or exciting cause of pancreatitis, 
as the bile may flow backwards along the pancreatic duct and 
damage the gland tissue. In the second place, obstruction 
to the outflow from the main pancreatic duct may be com- 
pensated for by the dilatation of a connexion which some- 
times exists between the main duct of the pancreas and an 
accessory duct. The latter is confined to the head of the gland 
and it opens into the duodenum by a separate orifice, placed 
a short distance above the ampulla of Vater (Fig. 98). 

The Lymph Vessels of the pancreas terminate in the coeliac 
glands (p. 249), after passing through the subpyloric, pancreatic 
and other subsidiary groups. The occurrence of secondary 
deposits in the pancreas following primary cancer of the 
stomach has already been mentioned. 

Development of the Pancreas. — The presence of two 
pancreatic ducts, both opening into the duodenum, is explained 
on reference to the developmental history of the gland. Shortly 
after the appearance of the diverticulum which forms the liver 
(p. 264), two similar diverticula grow out from the ventral 
surface of the duodenum, and one of these normally disappears. 
The other, which is situated at the point where the liver 



270 THE DIGESTIVE SYSTEM 

diverticulum is connected to the duodenum, rapidly proliferates 
and forms the head of the gland and the terminal part of the 
main duct. 

About the same time, a similar diverticulum grows out from 
the dorsal surface of the duodenum to form the body and tail 
of the gland. The ventral and dorsal diverticula approach 
one another and become fused. Their ducts become con- 
nected in such a way that the main pancreatic duct is formed 
by the distal portion of the dorsal duct and the whole of the 
ventral duct, and it therefore opens into the duodenum in 
common with the bile duct. The proximal part of the dorsal 
duct retains its own connexion with the duodenum and 
persists as the accessory duct of the pancreas. A trace of 
this developmental change may or may not persist in the 
presence of a connexion between the accessory and the main 
pancreatic ducts. 

Annular pancreas is a rare congenital anomaly. Normally, 
the margins of the head of the pancreas overlap the medial 
border of the second part of the duodenum both anteriorly 
and posteriorly. These overlapping edges may become so 
increased in extent that they meet one another at the lateral 
border of the duodenum, and thus form a complete circle 
round the gut. The condition may give rise to no symptoms 
whatever, but, if the gland becomes the site of inflammatory 
changes, serious obstruction of the duodenum will result. 

The Pancreatic Secretion contains three important enzymes, 
which act on the proteid, the fatty and the carbohydrate 
elements of the food. The flow of pancreatic juice commences 
when the acid contents of the stomach are expelled into the 
duodenum. In the presence of an acid medium, the duodenal 
mucous membrane secretes a substance, termed secretin, 
which becomes absorbed into the blood-stream and eventually 
reaches the pancreas, where it causes a rapid flow of the 
pancreatic secretion. It follows, therefore, that a diminution 
in the acidity of the stomach contents is accompanied by a 
diminution in the pancreatic secretion. Under these circum- 



THE PORTAL CIRCULATION 271 

stances, digestion is interfered with both in the stomach and 
in the duodenum. 

In the absence of the pancreatic secretion, e.g., pancreatic 
infantilism, and in obstruction to the outflow of the secretion 
into the duodenum, the most striking feature is due to the 
absence of the lipolytic enzyme. The digestion of fatty 
substances is impossible and these constituents of the food 
are passed unchanged in the faeces. The digestion of proteins 
and carbohydrates is not so seriously disturbed, as they are 
acted on by the saliva, the gastric juice and the succus 
entericus. 

At birth, the amylolytic action of the pancreatic secretion 
is not well developed, although its proteolytic and lipolytic 
actions are quite normal. When it is remembered that the 
saliva has little action on carbohydrates during the first year, 
it becomes quite evident that starchy foods should not form 
a part of the diet of the infant. 

In addition to the secretion which it pours into the intestine, 
the pancreas possesses an internal secretion. This secretion 
is formed by groups of polygonal cells, termed the " islands of 
Langerhans," which have no connexion with the ducts of the 
gland. It has been suggested that diabetes mellitus is due to 
insufficiency of the pancreatic internal secretion and the 
"islands" are found to be degenerated in a certain percentage 
of cases. 

The Portal Circulation 

A special description of the portal vein and its tributaries 
is rendered necessary owing to the frequency with which portal 
obstruction occurs and owing to the important changes which 
result from such obstruction. 

The Portal Vein is formed by the union of the superior 
mesenteric and the splenic vein behind the neck of the pancreas. 
From its origin it passes upwards, lying at first in front of the 
head of the pancreas and later behind the first part of the 
duodenum, where it comes into relationship with the bile 



272 THE DIGESTIVE SYSTEM 

duct (p. 262). At the upper border of the duodenum, the 
vein enters the lesser omentum, in which it ascends to the 
porta hepatis (transverse fissure of the liver) in company with 
the bile duct and the hepatic artery (PI. I.). 

At the porta hepatis, the portal vein divides into right and 
left branches, which enter the right and left lobes of the 
liver, respectively. These branches eventually break up into 
capillaries, and thus the blood of the portal circulation passes 
through two sets of capillaries before it finally returns to the 
heart. 

The effects of portal obstruction can be fully appreciated 
only after a study of the organs which drain their blood into 
the portal circulation. 

The Superior Mesenteric Vein receives tributaries from the 
following sources: — (1) The terminal part of the duodenum 
and the whole length of the jejunum and ileum ; (2) the 
caecum and the vermiform process (appendix) ; (3) the 
ascending colon and rather more than the right half of the 
transverse colon ; and (4) the greater curvature of the stomach, 
through the right gastro-epiploic vein. 

The Splenic Vein commences at the hilum of the spleen, 
where the veins which issue from that viscus are joined by 
the left gastro-epiploic vein, from the greater curvature, and 
some small veins from the fundus of the stomach. It passes 
to the right behind the pancreas and receives numerous 
pancreatic veins. In addition, the splenic vein is joined by 
the inferior ynesenteric vein, which receives tributaries from — 
(1) the left half of the transverse colon; (2) the descending colon ; 
(3) the iliac colon; (4) the pelvic colon ; and (5) the rectum. 

The portal vein itself receives tributaries from — (1) the 
lesser curvature of the stomach ; (2) the head of the pancreas 
and the duodenum ; and (3) the gall-bladder. 

When these various tributaries are summarised, it is 
found that the portal system drains the spleen, the pancreas, 
the gall-bladder and the whole of the abdominal part of 
the alimentary canal with the exception of the anal canal. 



THE PORTAL CIRCULATION 



273 




Fig. 100.— The Portal Vein and its Tributaries. (Turner's Anatomy.) 



1. Portal vein. 

2. Right branch of portal ; 

vein. 

3. Left branch of portal vein. 

4. Left gastric (coronary) 

vein. 

5. Rightgastro-epiploicvein. 

6. Splenic vein. 

7. Superior mesenteric vein. 

8. Right colic vein. 

9. Ileo-colic vein. 



10. 


Intestinal veins. 


S- 


Ascending colon. 


II. 


Inferior mesenteric vein. 


h. 


Descending colon. 


I 2. 


Left colic vein. 


k. 


Pelvic colon. 


13- 


Superior hemorrhoidal 


1. 


Rectum. 




vein. 


in. 


Gall-bladder. 


a. 


Liver. 


n. 


Cystic duct. 


b. 


Stomach. 


0. 


Hepatic ducts. 


c. 


Duodenum. 


A 


Bile duct, termination of. 


d. 


Pancreas. 


9- 


Pancreatic duct. 


e. 


Spleen. 


r. 


Hepatic artery. 


/■ 


Ileum. 


s. 


Ligamentum teres. 



18 



274 THE DIGESTIVE SYSTEM 

These, then, are the viscera which will be affected primarily 
in portal obstruction. 

Portal Obstruction. — The portal circulation may be 
obstructed in the liver itself by hepatic cirrhosis — the 
commonest cause — or by tumours, either 'of liver or stomach, 
in the neighbourhood of the porta hepatis. More rarely, the 
portal vein may be obstructed by malignant disease of the 
head of the pancreas. Whatever the cause, the symptoms 
referable to obstruction of the portal circulation are always the 
same. The walls of the stomach become the site of venous 
congestion, the veins become dilated and some may rupture, 
causing haematemesis. A similar condition affects the walls 
of the alimentary canal, for the larger veins of the portal 
system do not possess any valves. On this account intestinal 
derangement, which is usually characterised by alternate 
periods of diarrhoea and constipation, is brought about and 
internal haemorrhoids are found in the lower part of the 
rectum. 

Backward pressure along the splenic vein causes venous 
congestion of the spleen, which usually becomes enlarged 
and may project from under the left costal margin. The 
increase in size of the spleen is one of the most constant 
concomitants of portal cirrhosis. 

Stasis of the mesenteric veins not only affects the intestinal 
canal, but it also causes an increased transudation of serum 
into the peritoneal cavity, and, as the peritoneal stomata 
(p. 240) are not able to remove it with sufficient rapidity, the 
condition of ascites is brought about. The subsequent action 
of the stomata is further hampered by a chronic thickening of 
the peritoneum, which usually accompanies the condition. 

Communications between the Portal and the Systemic 
Veins. — Although obstruction to the portal circulation is only 
completely compensated in exceptional cases, the condition is 
always accompanied by a dilatation of the normal channels 
of communication which connect the systemic to the portal 
system of veins. 



THE PORTAL CIRCULATION 275 

At the upper end of the abdominal alimentary canal, the 
left gastric (coronary) vein on the lesser curvature communi- 
cates with the oesophageal veins, which open indirectly into 
the superior vena cava. In portal obstruction this anastomosis 
becomes greatly dilated and may form varices in the lax 
submucous tissue of the lower part of the oesophagus. Rupture 
of these veins causes hcematemesis which may be the first 
sign of portal cirrhosis. 

At the lower end of the abdominal alimentary canal, the 
superior hemorrhoidal veins, which return their blood via 
the inferior mesenteric and splenic veins to the portal system, 
communicate freely with the middle and inferior haemorrhoidal 
veins, which open indirectly into the inferior vena cava. 
Dilatation of this anastomosis and the production of internal 
hcemorrhoids is favoured by — (1) the action of gravity, (2) the 
absence of valves, and (3) the fact that the radicles of the 
superior hemorrhoidal veins ascend in the submucous tissue 
of the rectum for some distance before piercing the muscular 
wall (p. 284). 

The mesenterie and splenic veins communicate with the 
veins of the posterior abdominal wall, which ultimately 
open into the inferior vena cava. It is said by some 
authorities that, in the rare event of complete compensation, 
it is this anastomosis which carries off by far the greatest part 
of the obstructed blood. 

An extremely interesting communication is established 
through the medium of the para-umbilical veins. These small 
vessels, which unfortunately are not always present, are con- 
nected above to the left branch of the portal vein and they 
descend on the obliterated umbilical vein (ligamentum teres, 
p. 260) to the umbilicus, where they establish communications 
with the superficial veins of the anterior abdominal wall 
(p. 316). When this anastomosis becomes dilated the super- 
ficial abdominal veins are rendered visible through the skin. 
They are large and tortuous, and they radiate from the 
umbilicus, so that the general appearance has been termed 



276 THE DIGESTIVE SYSTEM 

the caput Medusae. This condition must be compared 
with and distinguished from the somewhat similar condition 
induced by obstruction of the inferior vena cava (p. 316). 
In portal obstruction, the bloodstream flows away from the 
umbilicus. Some of the veins run upwards and laterally to 
end ultimately in the superior vena cava, while others pass 
downwards and laterally to join the femoral vein and so end 
in the inferior vena cava. The presence of the caput 
Medusa not only is diagnostic of portal obstruction but it 
is diagnostic of portal obstruction within the liver itself, for the 
upper end of the para-umbilical vein is connected to the left 
branch of the portal vein and, therefore, cannot be involved 
when the obstruction occurs below the porta hepatis (trans- 
verse fissure of the liver). 

The Large Intestine 

The Caecum. — The caecum is that part of the large intestine 
which lies below the termination of the ileum (Fig. 101). It 
forms a blind sac, about 2\ inches long and 3 inches wide, 
which occupies the right iliac fossa, and it can be mapped out 
on the surface in the area below the inter-tubercular plane and 
to the lateral side of the right lateral plane (Fig. 101). Under 
normal conditions, the caecum is completely invested by peri- 
toneum, and therefore enjoys a certain degree of mobility. 
The peritoneum on its anterior and lateral aspects is con- 
tinuous with the corresponding covering of the ascending colon, 
but the peritoneum on its posterior aspect is reflected back- 
wards from its upper end to the iliac fossa. 

So long as its muscular wall is healthy, the caecum does not 
extend beyond the right iliac fossa, but when the wall loses its 
tone, the caecum tends to sag downwards and medially over the 
brim of the pelvis. Lane suggests that this latter condition is 
by no means uncommon and that thickened bands, which pass 
upwards and laterally and upwards and medially, respectively, 
from the upper end of the caecum, are developed in an 



THE LARGE INTESTINE 



277 



endeavour to retain the caecum in its normal position. These 
bands may involve the vermiform process or the terminal part 
of the ileum and cause them to become kinked (p. 256). 

The Vermiform Process (Appendix) springs from the medial 
border of the caecum near its lower end. It is completely 
covered with peritoneum but differs from the caecum in that it 
possesses a mesentery, which contains the appendicular artery 
in its free border. The vermiform process is usually about 




Fig. ioi. — Anterior Aspect of the Trunk, showing the surface relations 
of the liver, the stomach and the large intestine. 

Note. — The reference lines are the same as those shown in Fig. 87. 



3 inches long, but it varies greatly in length and may measure 
from ij to 10 inches. Owing to its peritoneal relations, it 
possesses a wide range of movement and it is impossible to 
foretell where it will be found when an operation is performed 
for its removal. In certain cases of appendicitis, increased 
frequency of micturition is a prominent symptom, and it 
is held by some authorities that this condition only occurs 
when the vermiform process passes downwards into the pelvis 
and becomes adherent to the bladder. Another explanation, 
however, is possible, as will be shown later (p. 279). 



278 THE DIGESTIVE SYSTEM 

Development of the Caecum and Vermiform Process. — 
During the third week a localised dilatation appears on the anti- 
mesenteric border of the hind-gut (p. 286). After a time, the 
calibre of the proximal part of the dilatation increases in the 
same proportion as the rest of the intestinal tube, but the distal 
part remains relatively much smaller in diameter, although it 
continues to increase in length. This is the first sign of the 
formation of the vermiform process, which at first springs from 
the apex of the caecum. After birth, the lateral wall of the 
caecum grows much more rapidly than the medial wall, so that 
the vermiform process in the adult springs from the medial 
wall of the caecum and not from its apex. 

During the development of the caecum, the intestinal tube 
increases in length and forms a U-shaped loop, which is sus- 
pended from the posterior abdominal wall by a dorsal mesen- 
tery. The caecum lies on the distal limb of the U. The loop 
becomes rotated counter-clockwise through 180 , so that the 
distal limb of the U is carried across the anterior surface of 
the proximal limb. After this rotation of the gut has taken 
place, the caecum lies in contact with the lower surface of the 
right lobe of the liver. At birth, however, it is found normally 
in the right iliac fossa, but, not infrequently, the caecum and 
vermiform process are found at operations in the infra-hepatic 
position. 

The Nerve-supply of the Cecum and the Vermiform 
Process is derived from a number of sympathetic nerves 
which accompany their arteries of supply. These nerves have 
their centres in the region of the eleventh thoracic segment of 
the spinal medulla. 

In the early stages of appendicitis the pain is usually 
experienced in the median plane, at or just below the umbili- 
cus, and it is perfectly clear that we are here dealing with an 
example of the viscero-sensory reflex (p. 192). The abnormal 
afferent stimuli may " overflow " from the eleventh segment 
and affect the adjoining segments. As a result, the pain is not 
confined to the area supplied by the eleventh intercostal nerve, 



THE LARGE INTESTINE 279 

but it is also experienced in the areas supplied by the tenth and 
twelfth thoracic nerves. 

At a later stage, the most acute pain is experienced over 
M'Burney's point, which lies on the right lateral plane 1 inch 
below the intertubercular plane and corresponds to the point 
where the vermiform process springs from the caecum. At 
this point, too, there is usually tenderness to deep pressure. 
It is by no means certain whether these pains are actually felt 
in the viscus or whether they are felt in the abdominal wall. 
It is said that in cases of appendicitis, in which the vermi- 
form process has been subsequently found in the infra-hepatic 
position, there is no pain or tenderness over M'Burney's 
point, but these cases are not of frequent occurrence and 
they have not yet received sufficient attention. 

Cases of appendicitis may give rise to the viscero-motor 
reflex. This is represented by a localised contraction of the 
lower parts of the lateral abdominal muscles. It is curious 
that these areas of muscular contraction usually overlie the 
affected viscus, for, as already mentioned, the vermiform pro- 
cess develops in the median plane and its position in the 
right iliac region is assumed some months after it has received 
its nerve-supply. 

In pathological lesions of the csecum or the vermiform pro- 
cess, slight tonic contraction of the right psoas major may 
occur, as evidenced by slight flexion of the hip-joint. The 
muscle lies to the medial side of the csecum, and it is possible 
that it is only affected when its sensory nerves are irritated, 
e.g., by the presence of an abscess. Mackenzie believes that 
the condition may be accounted for by the presence of a 
" focus of irritation " in the spinal medulla, and he suggests 
that the frequency of micturition, associated with some cases 
of appendicitis, may be explained in the same way. 

The mucous membrane of the caecum and the vermiform 
process is richly provided with lymphoid tissue, and these 
parts of the intestinal canal may, therefore, be the site of 
ulceration and, sometimes, perforation in typhoid fever. 



2 8o THE DIGESTIVE SYSTEM 

The Colic (Ileo-csecal) Valve guards the opening of the 
ileum into the caecum and prevents the regurgitation of the 
contents of the caecum into the ileum. It can be indicated 
on the surface of the body at the intersection of the inter- 
tubercular and the right lateral planes (Fig. 101). 

The Ascending Colon begins at the upper end of the caecum 
and passes upwards on the posterior abdominal wall till it 
reaches the inferior surface of the right lobe of the liver, 
where it bends forwards and to the left, forming the right 
{hepatic) flexure of the colon. It is about 6 inches long and 
it lies behind the peritoneum, save in exceptional cases where 
it possesses a dorsal mesentery. 

This part of the colon can be mapped out on the surface 
to the lateral side of the right lateral plane, and it extends 
from the intertubercular plane to the ninth costal cartilage 
(Fig. 101). 

The Right Colic Flexure is placed under cover of the right 
costal margin. Posteriorly it lies on the right kidney, and 
anteriorly it is related to the liver and the gall-bladder. In 
this situation the colon and the gall-bladder may become 
adherent to one another following cholecystitis, and gall-stones 
may find their way into the gut and be discharged per anum. 

The Transverse Colon is about 20 inches long and it forms 
a U-shaped loop, which is suspended from the posterior 
abdominal wall by the transverse mesocolon. 

It extends from the right flexure to the left (splenic) 
flexure of the colon, both of which'are, within limits, fixed in 
position. The transverse colon, however, by virtue of its 
mesentery, may alter its position from time to time and, in 
radiograms taken in the vertical posture, its lowest point is 
usually a little above the upper border of the pubic 
symphysis, but it may descend still farther without justifying 
a diagnosis of viscero-ptosis. 

When the patient is in the dorsal decubitus, the transverse 
colon may be indicated as a widely open U. The lower 
border lies at, or a little below, the umbilicus, while the left 



THE LARGE INTESTINE 281 

extremity passes upwards under cover of the costal margin for 
an inch or more above the transpyloric plane and immediately 
lateral to the left lateral line (PL II.). 

Above, the transverse colon is related to the stomach, and 
the interposition of a dull area between the two is suggestive 
of pancreatic cyst or tumour. 

The Descending Colon is only about 4 inches long and is 
entirely retro-peritoneal. It extends vertically downwards from 
the left colic flexure to the iliac crest, and it is placed more 
deeply in the abdominal cavity than the ascending colon, 
being separated from the anterior abdominal wall by coils of 
small intestine. 

The Iliac Colon runs downwards and medially across the 
left iliac fossa, from the iliac crest to the brim of the pelvis. 
In its lower portion it lies parallel to and a little above the 
lateral half of the inguinal ligament (of Poupart). Normally, 
coils of small intestine intervene between the iliac colon and 
the anterior abdominal wall, but tumours of this part of the 
bowel can be palpated when deep pressure is used, owing to 
the resistance offered by the ilium. 

The Pelvic Colon varies considerably in length, but it 
always possesses a definite mesentery. It may be as short as 
6 and as long as 16 inches, and its coils usually lie within 
the pelvis in relation to the rectum, the bladder and the 
terminal coils of the ileum. 

The Rectum, which is about 5 inches long, commences 
opposite the third sacral vertebra, where it is continuous 
above with the pelvic colon. In its upper third, it is covered 
with peritoneum anteriorly and on each side ; in its middle 
third, it is covered only on its anterior aspect. At the junction 
of the middle and lower thirds of the rectum, the peritoneum 
passes forwards, forming the floor of the pelvic compartment 
of the peritoneal cavity, and reaches the bladder, in the male 
(the upper part of the posterior wall of the vagina in the 
female, Figs. 127 and 134). The lower third of the rectum is 
therefore devoid of peritoneal covering. 



282 



THE DIGESTIVE SYSTEM 



As it descends through the pelvis, the rectum follows the 
curve of the sacrum and coccyx, and i inch in front of the tip 
of the coccyx it bends sharply backwards and downwards to 
join the anal canal. When it is examined in situ from in 
front it is found that the rectum bulges to the left side of the 
median plane. It possesses three lateral flexures. At first it 
bends to the left and then to the right, so as to regain the 




Fig. 102. — The Rectal Valves. 

An oblique frontal (coronal) section has been made through the pelvis so as to pass 
through the anal canal. In addition, the anterior wall of the rectum has been 
removed and the rectal valves (x) are exposed. The lateral flexures of the 
rectum are well shown. 



median plane, but it does not pass over to the right side. 
Instead, it bends for a third time, so that its lower part lies in 
the middle line. On the concave side of the lateral flexures, 
the mucous membrane projects into the lumen of the gut 
forming horizontal folds, termed the rectal valves. The 
highest and the lowest of the three lie on the left wall of the 
gut, while the middle valve lies on the right wall. The lowest 
valve can be reached with the tip of the finger on rectal 



THE LARGE INTESTINE 28 



o 



examination. When the rectum becomes distended, the valves 
form shelf-like ledges, which help to support the contents. 

Posteriorly, the rectum lies in contact with the sacrum and 
coccyx, against which scybalous masses may be compressed 
and broken down. The large nerve trunks which form the 
left sacral plexus lie behind the rectum, before they leave the 
pelvis to enter the gluteal region. When the rectum is greatly 
distended, it may overlap and compress both sacral plexuses. 
As a result of this pressure, painful symptoms are experienced 
in the back of the thigh and the condition may be mistaken 
for true sciatica (p. 182). Complete evacuation of the bowel, 
however, effects a speedy cure in these cases. 

Anteriorly, the rectum is related to the posterior surface of 
the bladder, the terminal parts of the ductus deferentes (vasa 
deferentia), the seminal vesicles and the prostate. All of 
these structures can be palpated on digital examination of the 
anterior wall of the rectum. (The examination of the rectum in 
the female is referred to on page 388.) 

The terminal part of the rectum is supported by the levatores 
ani muscles (p. 1S4), which separate it, on each side, from the 
ischio-rectal fossa. 

In rapid wasting conditions in childhood, the amount of fat 
in the ischio-rectal fossae is much diminished, and the rectum 
thus loses a certain amount of support. As the curvature of 
the sacrum is less pronounced in the child than in the adult, 
prolapse of the rectum may occur in these cases during violent 
straining efforts to empty the bowel. 

The Anal Canal passes downwards and backwards through 
the floor of the pelvis to open on the surface of the perineum. 
The mucous membrane lining the upper part of the anal canal 
is continuous with the mucous lining of the rectum and is 
characterised by numerous longitudinal ridges, which are united 
at their lower ends by transverse folds termed the anal valves. 
During the passage of a scybalous mass one of the little 
pockets formed by the valves may be torn, and this laceration 
constitutes the condition which is termed anal fissure. 



284 THE DIGESTIVE SYSTEM 

The lower part of the anal canal is lined by modified skin. 
This difference in structure indicates a difference in develop- 
mental origin (p. 287), and is characterised by a difference in 
nerve-supply. Thus, the upper part of the anal canal is 
supplied through the sympathetic system, while the lower part 
is supplied by the pudendal (internal pudic) nerve (p. 183). 

The Hemorrhoidal Venous Plexus is situated in the sub- 
mucous tissue of the anal canal. The importance of this 
plexus depends on the fact that it constitutes a free communica- 
tion between the superior hemorrhoidal vein, which passes, 
via the inferior mesenteric and the splenic, to the portal vein, 
and the middle and inferior hemorrhoidal veins, which pass 
via the hypogastric (internal iliac) and common iliac veins to 
the inferior vena cava. 

The superior hcemorrlioidal vein ascends for some distance in 
the submucous tissue of the rectum before it pierces the 
muscular wall of the gut, and it is, therefore, subjected to 
compression during defalcation. In portal obstruction (p. 274) 
or in chronic constipation, the blood is dammed back in the 
superior hemorrhoidal vein and the pressure in the hemor- 
rhoidal plexus is greatly increased. As the submucous tissue 
in which they lie is very distensible, the veins of the plexus 
become varicose and constitute the condition known as 
internal hemorrhoids. 

Irrigation of the Large Intestine is frequently necessary in 
children suffering from epidemic enteritis, and.it is important 
that the gut should not be overdistended by the introduction 
of more fluid than it can contain without dilating. Holt 
estimates that at six months the colon will hold not more than 
1 pint, while at two years z\ to 3 pints can be introduced 
without distending the gut. 

The Nerve-supply of the Large Intestine. — The large 
intestine, from the cecum to the pelvic colon, inclusive, is 
supplied by sympathetic nerves which have their centres 
situated in the lower thoracic and upper lumbar segments of 
the spinal medulla. The rectum receives some fibres from the 



THE LARGE INTESTINE 285 

same source, but, like the urinary bladder (p. 371), it is also 
supplied by sympathetic fibres which have their centres situ- 
ated in the mid-sacral segments. The latter fibres constitute 
the pelvic splanchnics of Gaskell and they also supply the 
upper part of the anal canal. On the other hand, the lower 
part of the anal canal is supplied through the cerebro- 
spinal system by the pudendal nerve (S. 2, 3 and 4). 

Violent peristalsis of the large intestine, such as occurs in 
griping, gives rise to pain, which is often referred to the 
peripheral distribution of the anterior rami (primary divisions) 
of the eleventh and twelfth thoracic and the first lumbar 
nerves, and especially to their anterior cutaneous branches 
(Fig. 69). It is consequently experienced most acutely in 
the hypogastric region, though it may also be referred to the 
iliac regions and the lateral part of the buttock. 

In new growths or ulceration of the rectum, pain is frequently 
referred to the perineum or to the back of the sacrum, and, in 
rare cases, it is experienced in the back of the thigh. Reference 
to Figs. 69 and 74 will show that these cutaneous areas are 
supplied by spinal nerves which all arise from the same seg- 
ments of the spinal medulla. Further, these segments also 
give rise to the pelvic splanchnics, which supply the rectum. 

The extreme tenderness of the anal canal in the presence of 
a fissure is purely local, for, since it is the lower part of the 
canal which is abraded in this condition (p. 283), the sensory 
branches of the pudendal nerve are directly stimulated. The 
accompanying contraction of the sphincter ani externus, which 
is also supplied by the pudendal nerve, is a good example of 
the viscero-motor reflex. 

Developmental Anomalies of the Intestinal Canal. 
— Atresia ani and the presence of some form of Meckel's 
diverticulum are the two commonest congenital abnormalities 
met with in the alimentary canal. 

At an early stage the primitive alimentary canal consists of 
a simple tube, closed at both extremities but open on its 
ventral aspect, where it communicates with the yolk-sac 



286 



THE DIGESTIVE SYSTEM 



(Fig. i). This connexion, which is termed the vitello- 
intestinal duct, becomes relatively smaller, as the gut increases 
in length, and it normally becomes obliterated entirely. It 
may, however, persist, and the highest degree of persistence 
consists in the presence at birth — after the' umbilical cord has 
been divided — of an umbilical frccal fistula. In the com- 
monest variety, the proximal part of the duct remains as a 
short blind diverticulum on the anti-mesenteric border of 
the ileum about 3 feet from its termination. This variety of 






4 7 

1 11. in. 

Fig. 103. — The Development of the Bladder and Rectum. 

In I., the cloacal membrane is just beginning to form. In II., it is very extensive, and 
the cloaca is being divided into ventral and dorsal portions. In III., the bub-division 
of the cloaca is complete and the uro-genital and anal membranes have ruptured. 



1. Hind-gut. 
z. Allantois. 

3. Cloacal membrane. 

4. Cloaca. 



5. Genital tubercle. 

6. Ventral, urinary, part of 

cloaca. 

7. Dorsal, gut, part of cloaca. 



8. Perineal orifice of uro- 

genital sinus. 

9. Anal orifice. 



persistent vitello-intestinal duct constitutes a Meckel's diverti- 
culum, and it is of importance because it may become adherent 
to the mesentery and give rise to intestinal obstruction. 

The blind posterior part of the primitive alimentary canal 
is known as the hind-gut. A small diverticulum, termed the 
allantois, passes from the ventral wall of the hind-gut, near 
its cephalic extremity, into the body-stalk (Fig. 103). The 
part of the hind-gut which lies caudal to the allantois is termed 
the cloaca, and it subsequently becomes divided into a ventral 
or urinary, and a dorsal or intestinal, segment. While this 



THE LARGE INTESTINE 287 

subdivision is in progress, the mesoderm separating the ventral 
wall of the cloaca from the ectoderm disappears over an area 
which is termed the cloacal membrane. 

When the subdivision of the cloaca is completed, it is found 
that the cloacal membrane also has been divided into two 
corresponding parts, which are termed the urogenital and 
anal membranes, respectively. The anal membrane becomes 
depressed to form the proctodeum and it finally breaks 
down, so that the anal canal opens on the surface of the body 
(Fig. 103). During the subdivision of the cloacal membrane, 
the mesoderm grows into the central area so as to separate the 
urogenital and anal membranes from one another. If it grows 
in between the ectodermal and endodermal layers of the anal 
membrane, the membrane fails to break down and the condition 
of atresia ani results. 

It will be seen from Fig. 103, III., that the lining of the 
upper part of the anal canal is derived from entoderm, while 
that of the lower part is derived from ectoderm. 



IV 

THE VASCULAR SYSTEM 

The Pericardium. — The Pericardium is a fibro-serous sac 

which encloses the heart and the roots of the great vessels. 

It is shaped like a truncated cone, the base being directed 

downwards and the apex upwards. Inferiorly, the outer 

fibrous layer of the pericardium is blended with the central 

tendon of the diaphragm, so that the possible amount of 

lateral displacement of the heart is strictly limited. As the 

great vessels pierce the pericardium, the fibrous layer is 

prolonged upon them for varying distances. On the aorta, 

it becomes blended with the pretracheal layer of the deep 

cervical fascia, which descends into the thorax on the anterior 

aspect of the trachea. This connexion may, perhaps, help to 

produce the clinical phenomenon of " tracheal tugging," which 

is found in association with aneurisms of the aortic arch (see 

also p. 321). 

The serous pericardium consists of a parietal layer which 

lines the fibrous pericardium, and a visceral layer which 

is reflected on to the heart and constitutes the epicardium 

(Fig. 104). In this way, the heart is enveloped in a completely 

closed serous sac, so that its action becomes greatly impeded 

when the sac is distended by effusions. As the aorta and 

pulmonary artery leave the heart, they are surrounded by a 

common tube-like continuation of the epicardium, about 1 inch 

long, which becomes continuous with the parietal layer of 

the sac. The superior vena cava does not possess a similar 

covering, and is only clothed on its anterior and lateral 

288 



THE PERICARDIUM 



289 



aspects by the serous pericardium. A small pocket of the 
pericardial sac, therefore, lies in front of the termination of 
the superior vena cava (Fig. 105), and, when it is distended 
with fluid, it may exercise pressure on the vessel, giving rise 
to venous engorgement on both sides of the head and neck 
and in both upper limbs. 

On each side, the pericardium is related to the medial 



, -Ascending aorta 

Transverse sinus 
j*""""'of pericardium 



Oblique sinus 
'of pericardium 



-Eplcardium 
-Serous layer 
of pericardium 
"Fibrous peri- 
cardium 




Fig. 104. — Diagram of a Sagittal Section through the Heart 
and the Pericardium. 



surface of the lung from which it is separated by the medi- 
astinal pleura. Pericardial effusions are sometimes so large 
that they may compress the lungs and so superimpose pul- 
monary dyspnoea on the existing cardiac dyspnoea. 

Posteriorly, the pericardium is related to the descending 
thoracic aorta and to the oesophagus, which intervene between 
it and the vertebral column. When food passes down the 
oesophagus, the tube is bulged forwards and pressed against 
the posterior aspect of the pericardium. In pericarditis, 

J 9 



290 



THE VASCULAR SYSTEM 



swallowing is often a painful process, and the pain is referred 
to the terminal branches of the upper intercostal nerves. The 
occurrence of this symptom in cases of acute rheumatic fever 
may be the first indication of pericardial involvement. 

Anteriorly, the pericardium is partly overlapped by the 
lungs and pleural sacs, but it is in direct contact with the 
sternum over a small area (Fig. 106). In young children the 




Fig. 105. — Diagram of a Transverse Section through the upper part 

of the Pericardium. 

The serous layer of the pericardium is represented by the dotted line. 



1. Pulmonary artery. 

2. Fibrous layer of pericardium. 

3. Ascending aorta. 

4, 5. Serous layer of pericardium. 



6. Superior vena cava. 

7. Right pulmonary vein. 

8. Transverse sinus of pericardium. 

9. Upper extremity of left atrium (auricle). 



dulness obtained on percussion over this area may be con- 
tinued upwards to the upper border of the sternum. This 
phenomenon usually indicates the presence of a large thymus 
(p. 413). The area of contact with the anterior thoracic 
wall becomes greatly increased in large effusions, owing to the 
retraction of the anterior borders of the compressed lungs. 
In these cases it may be possible to determine by percussion 
that the dulness extends over an area which corresponds to 
the conical shape of the pericardial sac. 



THE PERICARDIUM 291 

It should be remembered that large pericardial effusions 
thrust the heart forwards against the chest wall, so that the 
introduction of a cannula at the border of the sternum is 
certain to result in injury to the heart. The fluid collects 
posteriorly and on each side of the heart, and on this account 
the operation of paracentesis pericardii is best carried out at the 
left extremity of the dull area and through the fifth intercostal 
space. As a rule the instrument will pass through the left 
pleural sac, but this injury is not followed by any bad results. 
The instrument is thrust backwards and slightly medially, and 
its entry into the pericardial sac is indicated by the cessation 
of resistance to its passage. 

Inferiorly, the pericardium is supported by the diaphragm, 
which separates it from the upper surface of the liver. Peri- 
cardial effusions may displace the liver in a downward direction, 
so that its lower border may be palpated below the costal 
margin. 

Superiorly, the upper limit of the pericardial sac surrounds 
the ascending aorta and the pulmonary artery and comes 
into relation with the left bronchus. In pericardial effusions, 
the bronchus may be compressed, thus increasing the re- 
spiratory embarrassment, or it may be thrust upwards so as to 
compress the left recurrent (laryngeal) nerve, as it hooks round 
the inferior aspect of the arch of the aorta (Purves Stewart). 

In adhesive mediastinitis, the fibrous layer of the pericardium 
becomes firmly anchored to the sternum and costal cartilages 
in front and to the posterior thoracic wall behind. When the 
ventricles contract, the left interspaces are drawn inwards on 
the front of the chest, and a similar indrawing may be 
observed in the lower left interspaces on the dorsal aspect of 
the body. In this condition, the heart is called upon to work 
at an obvious disadvantage, and, in order that it may efficiently 
perform its functions, it requires to undergo a great amount of 
hypertrophy, which is usually accompanied by some degree of 
dilatation. 

On the other hand, adhesions arising within the pericardial 



292 THE VASCULAR SYSTEM 

sac, as a result of pericarditis, give rise to no characteristic 
signs beyond dilatation and hypertrophy of the heart. 



The Heart 

The Heart is situated within the pericardium in the middle 
mediastinum. Its posterior surface, which consists of the two 
atria (auricles), is placed opposite the fifth, sixth, seventh and 
eighth thoracic vertebrae and is separated from them by the 
pericardium, the cesophagus and the descending thoracic 
aorta. The antero-snperior surface is in relationship to the 
lungs and pleural sacs and to the anterior chest wall, and it 
is the outlines of this surface which are represented when the 
heart is mapped out on the anterior surface of the body. It 
comprises — (i) The right atrium, which occupies the right 
portion of the area; (2) the right ventricle, which forms the 
large central area ; (3) the left ventricle, which is only repre- 
sented by a narrow strip along the left border ; (4) the left 
auricle (auricular appendix), which forms the left upper 
corner of the surface. 

The inferior surface of the heart rests on the diaphragm, 
by which it is separated from the superior surface of the liver 
and the antero-superior surface of the stomach. It consists 
of a small portion of the right atrium, which is placed to the 
right and posteriorly, but most of the surface is formed by 
the ventricles. Hyperdistension of the stomach may influence 
the heart's action — (1) by mechanical pressure, and (2) refiexly, 
through the vagus nerves. 

The Right Atrium (Auricle) receives the blood from the 
great systemic veins and expels it through the right atrio- 
ventricular orifice into the right ventricle. The opening of 
the superior vena cava is placed at the right upper extremity 
of the atrium and is not guarded by a valve. The opening 
of the coronary sinus, which returns the blood from the heart 
wall, and the opening of the inferior vena cava are placed at 
the lower part of the chamber and both are guarded by slender 



THE HEART 293 

folds of endocardium, but these primitive valves are never 
competent to prevent regurgitation. 

On the posterior wall of the right atrium, which is formed 
by the interatrial (interauricular) septum, there is a definite 
oval depression, termed the fossa ovalis. This depression 
occupies the site of the foetal foramen ovale (p. 303), and a 
small slit-like opening is often found in its upper part, but 
usually it is not of sufficient size to have any pathological 
or clinical significance. 

The right atrio-ventricular orifice, when normal in size, 
admits the tips of three fingers. It is guarded by a valve of 
three cusps, which consist of folds of redundant endocardium. 
These folds hang down into the interior of the ventricle and 
give attachment to a number of fine tendons, termed chorda 
tendifiece, which are attached at their lower extremities to the 
apices of the papillary muscles. A fibrous ring surrounds the 
orifice and gives attachment to the upper borders of the cusps. 

The Right Ventricle receives the blood from the right 
atrium and pumps it along the pulmonary artery into the 
lungs. Its walls are roughened by numerous muscular bands 
which are known as the trabecules carnece. The most important 
of these bands are the papillary muscles, which are attached 
to the ventricular walls by their bases and give origin, at 
their apices, to the chordce tendinece. It is owing to the action 
of the papillary muscles that the tricuspid valve is able to 
prevent the regurgitation of blood from the right ventricle into 
the right atrium (p. 300). 

The Left Atrium receives the blood from the pul- 
monary veins and expels it through the left atrioventricular 
(mitral) orifice into the left ventricle. It is deeply placed 
and is hidden from view anteriorly by the ascending aorta 
and the pulmonary artery. 

The left atrio-ventricular orifice, when normal in size, 
admits the tips of two fingers. It is guarded by the bicuspid 
valve, which, save that it possesses only two cusps, corresponds 
in every way to the tricuspid valve. 



294 THE VASCULAR SYSTEM 

The Left Ventricle pumps the blood into the ascending 
aorta, and its walls, which possess trabecule earner, papillary 
muscles, etc., are very similar to those of the right ventricle, 
except that they are nearly three times as thick. 

The orifices of the pulmonary artery 'and the aorta are 
guarded by endocardial valves, which consist of three 
semilunar cusps. During ventricular systole, the cusps are 
pressed apart and separated, but during diastole they are 
thrust together across the orifice and so prevent regurgitation 
into the ventricles. 

Surface Relations of the Heart. — In mapping out the 
antero- superior surface of the heart, the identification of 
the individual ribs is essential. The union between the 
manubrium and the body of the sternum is marked by a 
transverse ridge, which can readily be felt through the skin. 
At the extremities of this ridge, which is termed the sternal 
angle (of Louis), the second costal cartilages articulate with 
the sternum and they can be identified, therefore, in every 
case. The third, fourth and fifth costal cartilages can be 
distinguished without difficulty, but it is not easy to identify 
the succeeding cartilages, as the spaces between them are 
much narrower. 

The right border of the heart can be mapped out by a line 
which commences above on the right third cartilage, and 
descends with a slight convexity to the right. Opposite the 
fourth intercostal space this line reaches its maximum distance 
— about 1 1 inches — from the median plane, and it terminates 
below on the sixth costal cartilage i inch from the median 
plane. This border is formed by the right atrium (auricle) 
alone. 

The inferior border of the heart can be represented by a 
line which begins at the lower extremity of the right border 
and passes to the left to reach the position of the apex-beat. 
Under normal conditions the apex of the heart lies in the fifth 
left intercostal space at a distance of 3^ inches from the 
median plane. The lower border of the heart is formed, for 



THE HEART 



295 



the most part, by the right ventricle, but its left extremity 
corresponds to a part of the left ventricle. 




[Photo ly A linari. 

Fig. 106.— Anterior Aspect of the Chest, showing the surface relations 

of the heart and great vessels, the lungs and the pleural sacs. 

Border of lung. 

Lines of pleural reflei tion. 

The left border of the heart can be represented by a line 
which begins at the apex and extends upwards and medially, 
with a gentle convexity to the left, to reach the lower part of 



296 THE VASCULAR SYSTEM 

the second left intercostal space, about half an inch from the 
left margin of the sternum. This line corresponds to the 
margin of the left ventricle, but at its upper end it outlines 
the left auricle (auricular appendix). 

The area which is mapped out by these borders corre- 
sponds to the antero-superior surface of the heart. The 
greater part of this surface is covered by the anterior margins 
of the lungs, but, owing to the presence of the incisura 
cardiaca (p. 349) on the left side, a small part is not covered 
by the left lung. This small area consequently yields a dull 
note on light percussion, and is termed the area of superficial 
cardiac dulness. It is roughly triangular in shape. Its right 
border is situated in the median plane and extends from the 
level of the fourth to the level of the sixth costal cartilage, a 
distance of about i\ inches. From this line the area of 
superficial dulness can be traced to the left, but it rapidly 
diminishes in vertical extent. The lower border of the area 
coincides with the intermediate portion of the lower border of 
the heart, and the upper border descends to meet it at a point 
about 1 inch medial to the apex-beat (Fig. 106). In map- 
ping out the area of superficial cardiac dulness very light 
percussion is employed, because of the thinness of the adjoin- 
ing lung margins. 

Although no part of the area of superficial cardiac dul- 
ness is covered by lung, that part of it which lies beyond 
the left side of the sternum is covered by the left pleural 
sac. 

Increase in the size of the area of superficial cardiac dulness 
may be due to one of several causes. Factors which tend to 
cause the lungs to retract or collapse, e.g. pulmonary tubercu- 
losis, pneumothorax, pericardial effusions, cardiac hypertrophy, 
etc., produce a real increase in extent. Left- or right-sided 
pleural effusions, when they rise as high as the sternal 
extremity of the fifth costal cartilage, increase the lateral 
extent of the area, but the increase is not a true increase inas- 
much as it is not formed by the heart. In young children, an 



THE HEART 297 

apparent increase in the vertical extent may be due to the 
persistence of a large thymus. 

Decrease in the size of the area of superficial cardiac 
dulness can only be due to one cause, namely, emphysema. 
This condition affects the least supported parts of the lungs, and, 
therefore, the thin anterior borders are always involved at an 
early stage. The margins of the incisura cardiaca are especi- 
ally liable to be involved, as they can be greatly distended 
without necessitating stretching of the parietal pleura 
(Fig. 106). 

With the exception of the area of superficial cardiac dulness, 
the whole of the antero-superior surface of the heart is covered 
by the margins of the lungs, which, in this situation, are not 
thick enough to obscure the dull cardiac note on firm per- 
cussion over the cardiac area. On this account, the position 
of the right and left borders of the heart can be determined 
by percussion, but it is practically impossible to determine 
the position of the lower border by percussion alone, as the 
dull cardiac note merges into the dull note of the liver. 

In dilatation or hypertrophy of the right ventricle the lower 
border of the heart is displaced in a downward direction. 
Although this alteration may not be easy to detect by means 
of percussion, inspection alone may be of great value in 
determining the condition. The downward enlargement 
produces well-marked pulsation in the epigastrium, and the 
character of the pulsation is quite different from that due to the 
abdominal aorta in neurasthenic patients or to aneurism of 
that vessel. In enlargement of the right ventricle, the 
collapse or recession of the epigastrium synchronises with 
ventricular systole, as it is due to the diminution of the 
chamber in volume during the contraction. On the other 
hand, in epigastric pulsation due to the abdominal aorta the 
forward movement of the epigastrium synchronises with 
ventricular systole. 

As the right ventricle enlarges, the left ventricle is displaced 
in a backward direction and the apex-beat can no longer be 



2g8 THE VASCULAR SYSTEM 

seen. Instead, there is a visible indrawing of the fourth and 
fifth intercostal spaces on the left side during systole, and this 
pulsation is similar in character to the pulsation in the 
epigastrium. This condition must be distinguished from the 
sucking in of the same interspaces caused by adherent peri- 
cardium (p. 291). 

Enlargement of the right ventricle is usually accompanied 
by an increase in size of the right atrium (auricle). Such an 
increase can be determined by percussion since it results in 
displacement of the right border to the right side, the left 
border remaining normal or being displaced to the left. 

It must be remembered that the heart may be thrust bodily 
over to the right by the pressure of a left-sided pleural effusion 
or pneumo-thorax, but in these cases the apex-beat is not 
found in its normal position and the left border of the heart 
is displaced medially. 

Enlargement of the left ventricle is indicated by displace- 
ment of the apex-beat downwards and to the left, while the 
distance of the left border of the heart from the sternum is 
found, on percussion, to be greater than normal. In this case, 
also, it must be remembered that the heart may be thrust over 
to the left by a right-sided pleural effusion or pneumothorax, 
but, under these circumstances, the position of the right 
border will be similarly altered. 

Dilatation of the left atrium (auricle) does not enlarge the 
area of cardiac dulness, unless the left auricle (auricular 
appendix) is affected, and, in that case, cardiac dulness may 
be discovered on percussion over the sternal end of the 
second left intercostal space. 

Unless coincident with pulmonary emphysema, the enlarge- 
ment of any of the chambers of the heart, except the left 
atrium, results in an increase of the area of superficial cardiac 
dulness, since the enlarging chamber pushes the lungs aside. 

In mapping out the antero-superior surface of the heart in 
the child, the methods indicated above may be followed, due 
allowance being made for the difference in size. Although, 



THE HEART 299 

in the adult, the apex-beat is found in the fifth intercostal 
space medial to the nipple line, in children under the age of 
four it is usually situated in the fourth intercostal space 
and it lies lateral to the nipple line. 

Surface Relations of the Valves of the Heart- — The 
pulmonary valve lies behind the upper border of the third 
costal cartilage of the left side, close to its articulation with 
the sternum, and the aortic valve lies on a level with the lower 
border of the same cartilage, but the latter lies nearer to the 
median plane. Thus the orifice of the pulmonary artery, 
which arises from the right ventricle, is situated to the left 
side of the orifice of the aorta, which arises from the left 
ventricle. This apparent contradiction is accounted for by 
the obliquity of the interventricular septum, which slopes 
backwards and to the right. 

The left atrio-ventricular (mitral) orifice is placed behind 
the left half of the sternum, opposite the sternal ends of the 
third interspace and the fourth costal cartilage, and it is dis- 
posed obliquely so that the blood is directed forwards, down- 
wards and to the left as it passes from the atrium into the 
ventricle. The right atrio-ventricular (tricuspid) orifice lies 
behind the right half of the sternum opposite the fourth cartilage, 
the fourth interspace and the fifth cartilage. 

The accurate topography of the valves themselves is not of 
very great importance in auscultation, as they are placed so 
close to one another that, on auscultation directly over them, 
it may be impossible to decide at which orifice a particular 
sound is produced. On this account, the sounds produced 
by the closing of the valves are ausculted over areas which 
are widely separated from one another, and which are placed 
over the chamber or vessel connected with the valve in 
question. 

The pulmonary area lies behind the sternal end of the left 
second interspace, and in this situation the pulmonary artery 
is separated from the surface only by the thin anterior border 
of the left lung. The aortic area lies over the right second 



3 oo THE VASCULAR SYSTEM 

costal cartilage at its junction with the sUrnum. This area 
projects a little to the right of the aorta, but overlaps the 
vessel at the point where it approaches most nearly to the 
anterior surface of the body. The tricuspid area, which is 
placed at the lower extremity of the sternum, is situated over 
that part of the right ventricle which is most remote from the 
other orifices. The bicuspid (mitral) area lies over the apex 
of the heart. In this position the left ventricle is very near 
the surface of the body, and the area itself is as far as possible 
from the other orifices. 

The Action of the Heart. — The rhythmical contractions 
of the heart begin in the atria at the orifices of the great veins. 
During atrial contraction the pressure in the ventricles under 
normal conditions is less than the pressure in the veins, and 
so the blood is forced into the ventricles. As the ventricles 
become filled, the cusps of the atrio-ventricular valves are 
floated upwards towards the orifices which they guard. Atrial 
systole is at once followed by ventricular systole and, as the 
intra-atrial pressure is less than the intra-arterial pressure, the 
force of the contractions tends to drive the cusps up into the 
atria. At the same time the papillary muscles contract and, 
through the chordae tendinere, retain the valve in place at the 
orifice. A brief period of rest, termed the cardiac diastole, 
follows the ventricular contraction, and then the cycle begins 
again. 

The two principal heart sounds which are heard on ausculta- 
tion are produced by the closure of the atrio-ventricular and 
the semilunar valves. The atrio-ventricular valves close at the 
commencement of ventricular systole, and, therefore, sounds 
which are produced during atrial systole will be heard immedi- 
ately prior to the first sound, e.g., the bruit of bicuspid or tri- 
cuspid obstruction. The semilunar valves, which guard the 
orifices of the aorta and pulmonary artery, close at the end of 
ventricular systole, and the bruits produced by regurgitation 
of blood through the aortic or pulmonary orifices occur at the 
commencement of diastole. 



THE HEART 301 



Ventricular systole causes a rise in the arterial blood- 
pressure which is marked in the sphygmographic tracing by the 
sudden upstroke (Fig. 107). At the end of ventricular systole, 
the semilunar valves close and the pressure begins to fall. But, 
as the valves close, the blood endeavours to pass back into the 
ventricles and it rebounds from the valves, causing a secondary 
increase in pressure, which is recorded on the tracing as the 
dicrotic wave. Thereafter the arterial pressure continues to 
fall during diastole and atrial systole. 

The orifices of the superior and inferior venae cava? are 
devoid of competent valves, and therefore a wave of increased 
pressure passes back along them with each atrial contraction. 
No valves are found in the superior vena cava or in the in- 



Fig. 107. — Sphygmographic Tracing of a Normal Pulse. 

nominate veins (p. 314), which form it, and so the impulse is 
transmitted to the subclavian and the internal jugular veins 
(p. 315). About 1 inch above the sternal end of the clavicle, 
the internal jugular possesses a valve of two crescentic cusps 
(Fig. 108), which is almost invariably competent. The portion 
of the vein below the valve is termed the jugular bulb, and, 
since it lies behind the interval between the sternal and the 
clavicular heads of the sterno-mastoid, it is readily accessible 
to the receiver of the sphygmo-manometer. This venous 
pulsation is perfectly normal, and tracings of it are of value in 
determining the condition of the heart (p. 311). 

The subclavian vein, which lies behind the clavicle and is 
consequently inaccessible, possesses no valves up to a point 
just distal to its reception of the external jugular vein. There- 



J02 



THE VASCULAR SYSTEM 



after, valves occur at intervals in the subclavian, axillary, and 
other veins of the upper limb. 

The external jugular vein, as a general rule, possesses a 
competent valve as it crosses the sterno-mastoid muscle. 
Since no valves intervene between this point and the right 
atrium (Fig. 108), venous pulsation may, under favourable 
conditions, be observed in the external jugular of a perfectly 
healthy subject. 

Development of the Heart. — In the young embryo, the 

Ext. Jug. Vein 




Fig. 108. — Diagram to show the positions of the valves on the 
tributaries of the Superior Vena Cava. 



heart consists of a contractile tube, which is separated into 
different parts by circular constrictions (Fig. 109). The large 
veins open into the sinus venosus, which is placed at the 
caudal (or posterior) end of the tube, and it pumps the blood 
headwards into the atrium. The ventricle lies in front of the 
atrium and conveys the blood to the truncus arteriosus, which 
is the most cephalad, or anterior, part of the primitive tubular 
heart. At this period of development, the heart receives its 
nerve-supply from the sympathetic system, and as a result the 
adult atria are supplied from a lower segment of the spinal 



THE HEART 303 

medulla than the adult ventricles, for the alteration in their 
relative positions occurs after the nerve-supply has been 
acquired. 

As the tubular heart grows in size, it becomes bent so that 
the atrial part passes forwards {i.e. towards the head) dorsal 
to the ventricular part. About this time, the single atrio- 
ventricular orifice becomes divided into two by the union of 
two endocardial cushions which project inwards from its 
margins. At the same time, septa appear in the atrium and 
in the ventricle and grow towards the linear partition which 

D 
C 
B 



Fig. 109. — Diagram of the primitive tubular Heart of the Embryo. 

A. Sinus venosus. C. Ventricle. 

B. Atrium. D. Bulbus cordis. 

separates the two atrio-ventricular orifices. Before the inter- 
atrial septum reaches the partition, it breaks down near its 
centre to form the foramen ovale, which remains patent till 
the end of fcetal life. The uppermost part of the inter- 
ventricular septum is the last part to form, and, consequently, 
is the commonest site for an abnormal communication between 
the two ventricles. This anomaly, however, is extremely rare. 
While the interventricular septum is in process of formation, a 
spiral septum arises which subdivides the truncus arteriosus 
into the aorta and the pulmonary artery. Owing to the fact 
that these two arteries are derived by subdivision from a 



3 04 THE VASCULAR SYSTEM 

common trunk, in the adult they remain enveloped by the 
same tubular sheath of serous pericardium (p. 288). 

The Circulation in the Foetus. — -The chambers of the 
foetal heart communicate with precisely the same blood-vessels 
as they do in the adult, but these vessels have, in some 
instances, rather different duties to perform. 

The pure blood returns from the placenta by the umbilical 
vein, which joins the left branch of the portal vein (Fig. no), 
and, if there were no "short circuit," it would require to pass 
through the liver before reaching the heart. A certain amount 
of the pure blood does enter the liver, and this fact accounts 
for the large size of that viscus in the new-born child. A 
"short circuit," however, is established by the ductus venosus, 
which connects the left branch of the portal vein to the 
inferior vena cava. In this way most of the pure placental 
blood passes directly from the umbilical vein to the inferior 
vena cava, where it becomes mixed with the impure blood 
returning from the abdomen and lower limbs. 

Thus the purest blood which enters the fcetal heart is 
poured into the right atrium (auricle) by the inferior vena cava. 
As it enters the atrium the blood-stream is directed by a fold 
of endocardium towards the foramen ovale in the inter-atrial 
septum, through which it passes to reach the left side of the 
heart. On the other hand, the impure blood carried by the 
superior vena cava is directed through the right atrio-ventricular 
orifice into the right ventricle. 

The purest blood which the fcetal heart distributes is pumped 
out by the left ventricle into the aorta, by which it is conveyed 
to the heart-muscle, the upper limbs, the head, neck and brain. 

Since the lungs of the foetus do not function, it is only 
necessary that they should be provided with sufficient blood 
for their own nourishment, but, despite this, the main stem of 
the pulmonary artery is so large that it does not require to 
dilate when the lungs become expanded by respiration. The 
surplus blood from the pulmonary artery passes into the aorta 
through a communication termed the ductus arteriosus. 



THE HEART 



305 



It is clear, therefore, that the abdominal viscera (with the 
exception of the liver) and the lower limbs will not be so well 
nourished at birth as the upper portion of the body. 

The hypogastric arteries, which arise from the common 



Superior_ _ 



vena cava 



Ductus venosus 



Portal vein 

Umbilical ve 




— — " Arch of aorta 
Ductus arteriosus 

V— I Pulmonary artery 



Hypogastric arteries 

Fig. no. — Diagram to illustrate the Fcetal Circulation. 

The course of the pure blood is indicated by the plain arrows ; the dotted arrows 
indicate the course of the impure or mixed blood. 

iliacs, pass up the anterior abdominal wall and enter the 
umbilical cord. They convey impure blood to the placenta 
from which it is returned, after being purified, by the umbilica 
vein. It may be noted that the umbilical cord contains two 
arteries but only one vein. 

Several important changes occur at birth. The expansion 
20 



306 THE VASCULAR SYSTEM 

of the lungs with respiration determines the flow of a larger 
quantity of blood to the lungs and causes an increased blood- 
pressure within the pulmonary artery, which drags on the 
ductus arteriosus. The latter is rendered oblique and soon 
becomes a fibrous cord, termed the ligamentum arteriosum. 
At the same time the foramen ovale closes, so that all direct 
communication between the right and left sides of the heart is 
cut off. 

After the ligature and division of the umbilical cord, the 
blood in the umbilical vein, from the umbilicus to the left 
branch of the portal vein, undergoes coagulation and the vessel 
itself becomes converted into a fibrous cord, termed the liga- 
mentum teres of the liver (p. 260). The ductus venosus 
becomes transformed in a similar manner, but the cause of 
this change is by no means clear. It has been suggested that 
icterus neonatorum may be due to patency of the ductus 
venosus. 

Congenital Anomalies of the Heart. — Congenital 
absence of the heart occurs in acardiac monsters, but the 
condition is of little interest to the clinician as it is never 
consistent with life. 

Dextro-cardia, or complete transposition of the heart, may be 
associated with a similar transposition of the abdominal viscera, 
and is always associated with transposition of the great vessels. 

Patency of the foramen ovale may occur without producing 
any characteristic signs. In these cases the opening, which is 
slit-like in character, is usually of small size, and, as it is 
provided with a valve-like arrangement, it possesses no clinical 
significance. A patent foramen ovale may, however, be associ- 
ated with other cardiac defects, such as imperfections of the 
upper part of the interventricular septum and patency of the 
ductus arteriosus. Although the child may be markedly 
cyanosed and loud heart murmurs may be present, there is 
seldom any enlargement of the left side of the heart and there 
may be little increase in the cardiac dulness to the right of the 
sternum. 



THE HEART 307 

Patency of the ductus arteriosus may occur alone. In this 
case much of the blood which was intended for the lungs is 
carried off by the ductus into the aortic system, so that there 
is diminished oxygenation, and, as a result, well-marked 
cyanosis is present. A loud bruit, systolic in time, is heard 
all over the prsecordia, but its point of maximum intensity is 
situated behind the left half of the sternum opposite the second 
intercostal space, i.e. over the pulmonary artery. The condi- 
tion may be distinguished from acquired aortic stenosis by the 
complete absence of any enlargement of the left ventricle. 

Congenital anomalies of the cardiac valves occur with much 
greater frequency on the right than on the left side of the heart, 
and the cusps of the semilunar valves are more commonly 
affected than those of the tricuspid valve. The cusps may be 
increased to four or five in number or decreased to two, but 
the condition is of no moment unless accompanied by stenosis 
of the pulmonary orifice. The latter condition is the com- 
monest variety of congenital heart lesion which is met with in 
practice, and it is marked by three cardinal signs — (a) Cyanosis ; 
(b) a loud systolic murmur with a weak second sound in the 
pulmonary area ; (c) enlargement of the right side of the 
heart. In many of these cases, the diminished flow of blood 
to the lungs determines the onset of pulmonary tuberculosis. 

Nerve-supply of the Heart. — The nerves which supply 
the heart are derived from the sympathetic system and from 
the vagi, through the superficial and deep cardiac plexuses. 
The sympathetic nerves have their centres in the spinal 
medulla in the upper four thoracic segments, and they pass 
into the upper four thoracic ganglia of the sympathetic in the 
white rami communicantes. They then ascend into the 
cervical portion of the sympathetic trunk and are given off as 
the cardiac branches of the cervical ganglia. The somewhat 
circuitous course which these fibres take is explained by the 
fact that, at the period when the heart receives its nerve- 
supply, it is situated in the cervical region. 

The Superficial Cardiac Plexus is placed immediately below 



3 o8 THE VASCULAR SYSTEiM 

the arch of the aorta, and it is formed by the union of a 
cardiac branch from the left vagus with a cardiac branch from 
the left sympathetic. A small ganglion is situated at the point 
where the two nerves unite and it is believed to control the 
rhythmical contractions of the heart, subject to the influence 
of stimuli from the higher centres. 

It should be observed that the superficial cardiac plexus is 
formed by branches from the vagus and the sympathetic, of 
the left side only. This arrangement may possibly account for 
the fact that the referred pains of angina pectoris are usually 
limited to the left side of the body. 

The Deep Cardiac Plexus lies in front of the bifurcation of 
the trachea and it is formed by branches from the sympathetic 
and the vagi, of both sides of the body. 

The fibres derived from the vagus are both afferent and 
efferent, the latter constituting the inhibitory nerves of the 
heart. Irritation of the vagus causes a slowing of the heart- 
rate, while paralysis leads to increased rapidity, since the 
sympathetic accelerator fibres are then no longer opposed. 

The sympathetic fibres also are both afferent and efferent, 
the latter constituting the accelerator nerves of the heart. In 
fracture-dislocation of the vertebral column in the lower 
cervical region, the sympathetic trunks are completely 
paralysed (p. 189), while the vagi are not affected. In this 
condition, therefore, there is usually a definite slowing of the 
heart-rate. 

Cardiac Pain. — When painful symptoms accompany 
cardiac disturbances they are usually severe and often agonis- 
ing in character. In the majority of cases of angina pectoris, 
the pain is experienced at first in the precordial region. It is 
at present impossible to decide whether the intense pain which 
is felt over the heart is actually experienced in the viscus, or 
whether, as Mackenzie holds, it is experienced in the sensitive 
tissues of the chest wall. In any case the pain is felt in the 
areas supplied by the upper intercostal nerves, and, since the 
sympathetic fibres which supply the heart are derived from 



CARDIAC PAIN 309 

the upper four thoracic segments, it is in these areas that 
referred pains might be expected to occur in cardiac 
disturbances. 

In later attacks of angina pectoris, the pain tends to radiate 
from the praecordia down the medial side of the left arm, and, 
in this case, there is no doubt that the condition exemplifies 
the viscero-sensory reflex (p. 192), since the painful areas are 
innervated by the first and second thoracic nerves (Fig. 67). 

If a " focus of irritation " (p. 195) is established in the upper 
thoracic segments of the spinal medulla, areas of cutaneous 
hyperalgesia (p. 195) may be found in the regions supplied by 
the nerves arising from the segments affected. In the same 
way, the muscles supplied by these segments may be very 
tender on deep pressure, and this muscular hyperalgesia is 
observed best in the pectoralis major and minor, which receive 
branches from the first thoracic nerve through the medial 
anterior thoracic nerves. In some cases where an area of 
cutaneous hyperalgesia is present, it is possible to induce a 
severe attack of cardiac pain by such a simple peripheral 
stimulus as lightly stroking the hyperaesthetic area. 

The posterior rami (primary divisions) of the upper thoracic 
nerves are much less frequently the site of referred cardiac 
pain than are the anterior rami. In angina pectoris, however, 
it is sometimes possible to demonstrate areas of hyperesthesia 
or hyperalgesia over the spines of the upper four thoracic 
vertebrae or in the adjoining region. 

Afferent impulses from the heart travel not only by the 
sympathetic but also by the vagus, and it is, therefore, possible 
for a " focus of irritation " to arise in the medulla oblongata 
in cardiac disturbances. The sensory nucleus of the vagus is 
practically continuous with the posterior column of grey 
matter in the spinal medulla, and a "focus of irritation" may 
spread downwards and cause an increased excitability of the 
sensory nerve-cells in the upper cervical segments. In angina 
pectoris, the pain may radiate into the left side of the neck 
and involve the areas supplied by the cutaneous branches of 



3 io THE VASCULAR SYSTEM 

the second, third and fourth cervical nerves (Fig. 69). It is 
probable that in these cases the stimuli reach the upper part 
of the spinal medulla by a downward spread from the lower 
extremity of the sensory nucleus of the vagus. Under these 
circumstances, the sterno-mastoid and the upper part of the 
trapezius are usually found to be tender to the touch, for these 
muscles, although receiving their motor supply from the 
accessory nerve, receive sensory branches from the cervical 
plexus (p. 128). 

The Cardiac Blood-vessels. — The heart is supplied by 
the right and left coronary arteries, which arise from the aortic 
sinuses (p. 318). The orifices of these vessels are so situated 
that the blood may have difficulty in entering them in 
atheromatous changes in the wall of the aorta near its origin 
or in the degenerative changes of the aortic valve which lead 
to aortic stenosis. Under these conditions, the muscular wall 
of the heart undergoes degeneration and the circulatory 
disturbance becomes more pronounced on that account. 

The veins of the heart join the coronary sinus, which pours 
its blood into the right atrium (auricle). 

The Musculature of the Heart. — The muscular fibres of 
the atria (auricles) pass uninterruptedly from the one atrium to 
the other, but, with the exception of the atrio-ventricular 
bundle (of His), they do not become continuous with the 
muscular fibres of the ventricular walls. Both atrial and 
ventricular fibres are attached to the fibrous rings which 
bound the atrio-ventricular orifices and constitute what 
Keith has termed the atrio-ventricular base of the heart. 

The primitive tubular heart of the embryo is so altered by 
the flexures which it undergoes that the atrio-ventricular 
orifices become placed side by side with the arterial orifices, 
and not, as in the embryo, at opposite ends of the ventricle. 
Keith believes that, as a result of these changes, the ventricular 
muscle fibres are so arranged that, when the ventricle contracts, 
the distance of the ventricular apex from the " aortic base " 
(arterial orifices) is unaltered, whereas its distance from the 



THE VENOUS PULSE 311 

atrioventricular base is definitely diminished. It follows 
that during ventricular contraction the apex may be regarded 
as a fixed point, although it moves upwards somewhat and 
presses against the anterior wall of the chest. On the other 
hand, the atrio-ventricular base, which constitutes the insertion 
of both the atrial and the ventricular fibres, moves with each 
atrial and with each ventricular contraction. As the orifices 
of the great veins are to be regarded as fixed points, the 
capacity of the atria becomes diminished with each atrial 
contraction. Ventricular systole pulls the atrio-ventricular 
base towards the apex and so increases the atrial capacity. 

V V * V V V V V ¥ V V * * v ■ * * ■ * * * * * r 








TkJuJ»s^ 



Fig. hi. — Tracing of the Normal Venous Pulse, together with 
a Synchronous Tracing of the Radial Pulse. 

The waves, v, a, and c, are referred to in the text. 

During diastole the atrio-ventricular base assumes a position 
of rest, mid-way between the positions which it occupies 
during atrial and ventricular contractions, respectively. 

This theory of the action of the cardiac musculature can be 
applied to the interpretation of the venous pulse. Atrial 
contraction causes a rise in the intra-atrial blood-pressure 
and prevents, for the time being, any further outflow from the 
veins. This condition is indicated by the upstroke of the 
venous pulse tracing (Fig. 111, a). The ensuing ventricular 
systole is marked on the tracing by the wave c. This does 
not indicate a true rise in the intra-venous blood-pressure but 
is transmitted from the common carotid artery. It is sue- 



312 THE VASCULAR SYSTEM 

ceeded by a marked fall in the pressure, since, during 
ventricular systole, the atrial walls are relaxed and the atrial 
capacity is further increased by the movement of the atrio- 
ventricular base towards the apex. The filling up of the 
atrium causes a rise in the intra-venous blood-pressure which 
is accentuated by the return of the atrio-ventricular base to 
the position of rest at the end of ventricular systole. The 
phase ceases when the tricuspid valve opens (Fig. in, v) 
and it is succeeded by atrial systole. This description only 
refers to the character of the venous pulse so long as the 
tricuspid valve is competent. 

In tricuspid incompetence, the right atrium has to deal 
with a larger quantity of blood and the pressure during atrial 
systole therefore rises to a higher level. Ventricular systole 
is accompanied by a fall in the pressure, but the succeeding 
secondary rise is hastened in its occurrence by the regurgitation 
into the atrium. Further, the fall in the secondary wave is 
less marked, as blood passes from the atrium into the ventricle 
during the whole of the diastolic period. This variety is 
referred to as the ventricular type of venous pulse. 

The Heart Rhythm.— In the primitive tubular heart, the 
rhythmical waves of contraction begin at the sinus venosus 
and pass to the atrium and ventricle by direct continuity of 
muscle fibres. In the adult heart the sinus venosus is in- 
corporated in the atria and most of the muscle fibres are 
interrupted at the atrio-ventricular base. It is believed that 
atrial contraction begins near the orifice of the superior vena 
cava in a specialised area, with distinctive histological 
characters, which has been termed the sino-atrial node. The 
wave of contraction passes by muscular continuity to the left 
atrium and it reaches a second specialised area, termed the 
atrio-ventricular node, which is situated on the inter-atrial 
septum near the atrio-ventricular base. From this node the 
atrio-ventricular bundle (of His), which is a collection of 
specialised muscle fibres, takes its origin, and it extends 
across the atrio-ventricular base into the interventricular 



HEART-BLOCK 



O T 1 

j J 3 



septum. It lies in that part of the septum which is covered 
by the posterior, or septal, cusp of the mitral valve, and, 
finally, divides into two parts, one for each ventricle. 
The exact destination of the terminal fibres is relatively 
unimportant. 

Under normal conditions the rhythmical contractions of 
the heart begin at the sino-atrial node, and, during atrial 
systole, they reach the atrio-ventricular node. From there 
the stimulus is conveyed along the atrio-ventricular bundle 
and causes ventricular systole. Each atrial systole is therefore 




Fig. 112. — Tracings from a case of Complete Heart-Block. 

The waves, a, correspond to the atrial contractions ; the waves, c, correspond to the 
ventricular contractions, as shown by the tracing from the radial pulse. 



followed immediately by a ventricular systole, so long as the 
conducting medium is able to perform its duty efficiently. 
Pathological lesions of the atrio-ventricular bundle may 
diminish its conductivity, and as a result each atrial systole is 
not immediately followed by a ventricular systole. In these 
cases, however, a summation of stimuli produces the effect 
which a single stimulus is insufficient to produce, and a ven- 
tricular systole follows every second or every third atrial 
contraction. This condition is known as Heart-block. A 
small lesion, involving the atrio-ventricular bundle before it 
divides, may cause complete heart-block, but a much larger 
lesion, involving one of its divisions, may give rise only to 



314 THE VASCULAR SYSTEM 

partial heart-block, or may produce no alteration at all in the 
heart rhythm. 

Although the heart rhythm normally commences at the 
sino-atrial node and is conveyed to the ventricle by the 
atrio-ventricular bundle, a complete lesion of the latter does 
not necessarily involve cessation of the ventricular contractions. 
Under these circumstances, ventricular contractions continue 
but they acquire a rhythm of their own, which is slower than, 
and quite distinct from, the atrial rhythm. Pulse tracings of 
this condition show that a ventricular contraction does not 
necessarily succeed an atrial contraction, but the two may 
occasionally be synchronous or the ventricular systole may 
precede the atrial systole. 

The Great Vessels 

The Superior Vena Cava is formed by the union of the 
right and left innominate veins, which unite with one another 
behind the sternal end of the first right costal cartilage. It 
descends, partly behind the sternum and partly projecting 
beyond its right border, to terminate in the uppermost part of 
the right atrium. Below the second costal cartilage, the vena 
cava is enclosed within the fibrous pericardium and it is 
related anteriorly to the serous pericardial sac. When the 
dulness to percussion produced by a pericardial effusion 
extends upwards into the right second intercostal space, the 
superior vena cava is usually compressed and the veins of the 
head, neck and upper limbs become greatly engorged. A 
similar condition is met with when the vena cava is com- 
pressed by an aneurism of the ascending aorta, which lies to 
its left side and on a slightly anterior plane. Such an 
aneurism may not only compress the vena cava but may 
subsequently rupture into it, giving rise to an arterio-venous 
aneurism, which is indicated by a sudden great increase in the 
already existing venous engorgement. 

The Innominate Vein is formed behind the sternal end of 



THE GREAT VESSELS 315 

the clavicle by the union of the internal jugular and subclavian 
veins. On the right side it descends vertically on the medial 
aspect of the apex of the right lung. It is only 1 inch in 
length and, therefore, it is rarely involved alone, as tumours 
which are of sufficient size to compress it are also large 
enough to affect the left innominate vein, either directly or 
indirectly through the superior vena cava. 

The left innominate vein passes to the right and downwards 
behind the upper half of the manubrium. It is about 3 inches 
long, and is consequently more exposed to pressure than the 
corresponding vein of the right side. In its course, it crosses 
the left subclavian, the left carotid and the innominate 
arteries close to their origin from the aortic arch, and it may 
therefore be compressed by aneurisms affecting this part of 
the aorta or the branches mentioned. It is placed behind 
the remains of the thymus, and it is characteristic of 
mediastinal tumours which originate from this developmental 
remnant that their pressure symptoms are first discovered in 
the engorgement of the veins of the left upper limb and the 
left side of the head and neck. 

The absence of valves from the superior vena cava and the 
innominate veins, and the venous jugular pulse, which is thus 
rendered possible, are referred to on page 301. 

The Inferior Vena Cava is formed at the right side of the 
fifth lumbar vertebra by the union of the two common iliac 
veins, which return the blood from the lower limbs and the 
pelvis. It ascends through the abdomen behind the peritoneum 
on the posterior abdominal wall, and, in its lower part, it is 
related anteriorly to the root of the mesentery (p. 240) and 
the coils of the small intestine. Opposite the third lumbar 
vertebra, the inferior vena cava is crossed by the third portion 
of the duodenum and, immediately above this level, it lies 
behind the head of the pancreas. In the latter situation, the 
vena cava may be compressed against the vertebral column by 
malignant tumours of the gland. Above the pancreas, the 
vena cava passes successively behind the first portion of the 



316 THE VASCULAR SYSTEM 

duodenum, the epiploic foramen (of Winslow) and the liver. 
It pierces the diaphragm opposite the fibro-cartilage between 
the eighth and ninth thoracic vertebrae and at once enters the 
lowest part of the right atrium (auricle) of the heart. 

As it ascends through the abdomen, the inferior vena cava 
receives numerous tributaries. Below the head of the 
pancreas, it is joined by the lower lumbar and the right 
spermatic (or ovarian) veins. As it lies behind the head of 
the pancreas, it receives both renal veins and, just before it 
pierces the diaphragm, it receives the right and left hepatic 
veins. 

The signs produced by obstruction of the inferior vena 
cava vary according to the site of the obstruction. When it 
is compressed near its origin, there may be little or no ascites 
and the venous stasis is most evident in the lower limbs. 
Swelling of the feet and ankles and dilatation of the superficial 
veins of the leg are always present. When the obstruction is 
very great, an effort is made to bring about compensation by 
the establishment of a new channel of return to the heart. The 
superficial veins of the lower part of the anterior abdominal wall 
pour their blood into the femoral vein, and so it ultimately 
reaches the inferior vena cava. On the other hand, the veins 
from the upper part of the anterior abdominal wall pour their 
blood into the intercostal and lateral thoracic veins, which are 
ultimately tributaries of the superior vena cava. These two 
groups communicate freely with one another, and, as they are 
devoid of valves and as the loose superficial fascia in which 
they lie permits of a large degree of dilatation, the anastomosing 
channels become greatly enlarged when the inferior vena cava 
is obstructed. In this condition, therefore, it is usually found 
that the superficial veins of the abdominal and thoracic walls 
are enormously dilated. The condition is somewhat similar 
to the " Caput Medusas " appearance found in portal obstruc- 
tion (p. 276), but presents this essential difference that, 
whereas in portal obstruction the blood-flow radiates in both 
directions from the umbilicus, in obstruction of the inferior 



THE GREAT VESSELS 317 

vena cava the direction of the blood-stream is upwards only, 
towards the superior vena caval system. 

The hepatic veins, which are the last tributaries received 
by the inferior vena cava, return the blood conveyed to 
the liver both by the hepatic artery and by the portal vein 
(p. 261). Regurgitation of blood into the inferior vena cava 
from the right atrium will therefore produce not only the signs 
of vena caval obstruction but also the signs of portal obstruc- 
tion. In this condition the effects are first to be observed in 
the liver, owing to the retardation of the outflow from the 
hepatic veins. The organ becomes greatly distended and 
projects downwards considerably beyond the costal margin. 
On palpation, pulsations are readily detected and, when they 
are carefully examined, they are found to occur just before the 
apex-beat. Tracings of the hepatic pulse correspond precisely 
to tracings of the jugular pulse, because they are both pro- 
duced in the same way. 

Unless the right atrium recovers its tone, other signs of vena 
caval obstruction follow dilatation of the liver. Owing to the 
retardation of the outflow through the renal veins and the 
consequent disturbance of the functions of the kidneys, the 
urine is scanty in quantity and contains albumen. The 
general venous congestion leads to an increased transudation 
of serum into the peritoneal sac and, as the stomata (p. 240) 
are unable to carry it away with sufficient rapidity, the con- 
dition of ascites develops. 

The Pulmonary Veins convey the oxygenated blood from 
the lungs to the left atrium. There are usually two on each 
side, but they may unite to form a common trunk before 
entering the heart. Dilatation of the left atrium (auricle) 
retards the outflow from the pulmonary veins, and, as a result 
of the venous congestion within the lung, an increased 
transudation of serum occurs into the pleural sacs. As this 
variety of hydrothorax is not inflammatory in origin, the fluid 
in most cases is not limited by adhesions, and it therefore 
gravitates down to the lowest recesses of the pleural sacs. 



318 THE VASCULAR SYSTEM 

Owing to the cardiac condition, the patient is usually in 
the dorsal decubitus or else in the semi-sitting posture, and 
the fluid therefore accumulates in the lower limit of the 
pleural sac posteriorly. 

The Ascending Aorta begins at the 'aortic orifice of the 
left ventricle and passes upwards, slightly forwards and to the 
right. Throughout its course it lies entirely behind the sternum 
and it approaches most nearly to the anterior surface of the 
body at its termination, which lies behind the right half of 
the sternum opposite the second costal cartilage. As the blood 
enters the ascending aorta from the left ventricle, it impinges 
on its right wall, and, as a result of this continually recurring 
pressure, the vessel is rendered oval instead of circular on 
transverse section. There is thus a normal dilatation, which, 
under certain circumstances, may become increased so as to 
constitute a pathological condition. 

Anteriorly, the ascending aorta is covered by the thin 
anterior borders of both lungs. When it is the site of aneur- 
ismal dilatation, it compresses the right lung and projects 
beyond the right border of the sternum. In this case, visible 
pulsations may be present in the right second intercostal space 
and the aortic sounds are heard with maximum intensity in that 
situation. As it bulges to the right, the ascending aorta may 
not only compress the right lung but also the superior vena 
cava, which lies along its right side and on a slightly posterior 
plane (Fig. 105). 

Close to its origin, the aortic wall presents three small dilata- 
tions, which are termed the aortic sinuses (of Valsalva). Each 
sinus is situated opposite a cusp of the aortic valve, and the 
right and left coronary arteries arise from the anterior and left 
posterior sinuses, respectively (p. 310). 

The Arch of the Aorta commences at the termination of 
the ascending aorta and, arching upwards, backwards and to 
the left, it reaches the left side of the body of the fourth 
thoracic vertebra, where it becomes continuous with the 
descending thoracic aorta. The backward inclination of the 



THE GREAT VESSELS 319 

arch is much more pronounced than its inclination to the left, 
and, as a result, almost the whole of the vessel lies behind 
the manubrium sterni (Fig. 106). 

At its commencement, the aortic arch occupies the interval 
between the two pleural sacs, but, in most of its course, it is 
covered by the left mediastinal pleura. As the left vagus and 
phrenic nerves descend through the thorax, they cross the 
vessel and intervene between it and the pleural sac. The 
left innominate vein crosses the branches of the aortic arch 
close to their origins, and it is therefore closely related to the 
upper border of the arch. 

The signs produced by an aneurism of the aortic arch 
depend partly on the direction in which it enlarges. When it 
does so in a forward direction, it compresses the left lung and 
comes into contact with the manubrium. The area of super- 
ficial dulness in this region becomes increased in size, and, as 
the aneurism enlarges, it may erode the sternum. At an early 
stage, however, it may be difficult to determine whether the 
dulness is due to aneurism or to a mediastinal tumour. The 
left vagus and phrenic nerves are more liable to be stretched 
than to be compressed, but they usually slip backwards over 
the aneurism, and their involvement can rarely be determined 
from the physical signs. 

Posteriorly, the aortic arch comes into contact successively 
with the trachea, the left recurrent nerve, the oesophagus, the 
thoracic duct and the vertebral column (Fig. 113). Any or all 
of these structures may be compressed, when an aneurism of 
the aortic arch enlarges in a backward direction. Pressure on 
the trachea results in respiratory discomfort and is indicated 
by the association of rales with the breath sounds. This sign 
may be accompanied by difficulty in swallowing, since the 
oesophagus passes downwards between the trachea and the 
vertebral column. The left recurrent nerve leaves the vagus 
at the lower border of the arch and hooks backwards and 
upwards behind the vessel to gain the groove between the 
trachea and the oesophagus. It is very commonly affected in 



320 



THE VASCULAR SYSTEM 



aneurisms of this part of the aorta and its compression is 
followed, in the first instance, by an abductor paralysis of 
the left vocal fold (true vocal cord, p. 338), which produces 




Fig. 113. — Transverse Section through the Thorax at the level of 
the fourth thoracic vertebra. 



I. 


Left vagus nerve. 


10. 


Trachea. 


2. 


Cardiac branch of sympathetic. 


11. 


Right vagus nerve. 


3- 


Cardiac branch of vagus. 


12. 


Right bronchus. 


4- 


Left phrenic nerve. 


13- 


Ridge indicating bifurcation of 


5. 


Descending aorta. 




trachea. 


6. 


Aortic arch. 


14. 


Left recurrent (laryngeal) nerve. 


7- 


Ascending aorta. 


15- 


Vena azygos. 


8. 


Superior vena cava. 


16. 


CEsophagus. 


9- 


Right phrenic nerve. 


17- 


Thoracic duct. 



strident breathing and a loud " brassy " note on coughing. 
At a later stage the fold may be completely paralysed. This 
condition is characterised by the toneless character of the voice 
{vox anserind) and by inability to cough in an efficient manner. 



THE GREAT VESSELS <s 2 i 



^ , 



Pressure on the thoracic duct is not easy to recognise, as the 
communications which it establishes with the right lymphatic 
trunk (p. 324) may dilate sufficiently to compensate for the 
obstruction. 

When the aneurism enlarges in an upward and backward 
direction, it may exert pressure on the upper part of the left 
sympathetic trunk (Fig. 49). As a result, the left pupil be- 
comes, at first, dilated and, later, contracted (p. 189). 

Erosion of the vertebral bodies is by no means uncommon, 
and the condition is accompanied by the characteristic pain of 
bone affections. Enlargement in a backward direction may 
bring the aneurism into relation with the intercostal nerves, as 
they pass forwards and laterally from the intervertebral foramina. 
The nature of the pain in this case is quite distinctive. It is 
radiating in character, and is referred to the peripheral distribu- 
tion of the anterior and lateral cutaneous branches. 

As the aortic arch passes backwards, it lies above the root 
of the left lung. Each pulsation of an aneurism of this part 
of the aorta thrusts the left bronchus in a downward direction, 
and this fact helps to account for the production of " tracheal 
tugging" (p. 288). 

Enlargement in an upward and forward direction will cause 
pressure on the left innominate vein with consequent venous 
engorgement of the left half of the head and neck and of the 
left upper limb. 

From the convex upper border of the aortic arch, three large 
branches arise, namely, the innominate, the left common 
carotid and the left subclavian arteries. 

The Innominate Artery arises in the median plane and 
passes upwards and to the right, on the anterior surface of the 
trachea, to terminate behind the right sterno-clavicular articula- 
tion, where it divides into the right subclavian and common 
carotid arteries. The relationship of this artery to the 
jugular (suprasternal) notch is somewhat variable, and, 
although usually placed at a lower level, it frequently rises 
so high that its pulsations can easily be felt in that region. 
21 



322 THE VASCULAR SYSTEM 

Aneurisms of the innominate artery, and aneurisms of the 
aortic arch which bulge upwards, also produce pulsations 
which are palpable and sometimes visible at the upper border 
of the manubrium sterni. 

The Descending Thoracic Aorta begins at the left side 
of the body of the fourth thoracic vertebra and inclines 
forwards to reach the median plane, so that, as it passes 
through the diaphragm, it lies in front of the vertebral column. 
This part of the aorta is closely related to the oesophagus. 
Above, the oesophagus lies to the right of the aorta and on a 
slightly anterior plane. As the vessel descends, it inclines 
medially, and it is crossed by the oesophagus just before it 
pierces the diaphragm. It is the latter situation which is 
the usual site of aneurisms of the descending thoracic aorta, 
and consequently these aneurisms are usually associated with 
marked difficulty in swallowing. 

The Abdominal Aorta begins at the aortic opening in the 
diaphragm and descends in front of the vertebral column. Its 
terminal bifurcation into the two common iliac arteries occurs 
opposite the left side of the fourth lumbar vertebra and corre- 
sponds, on the anterior abdominal wall, to a point a little 
below and a little to the left of the umbilicus. At first the 
abdominal aorta lies behind the posterior wall of the omental 
bursa, and then it descends behind the body of the pancreas, 
which crosses the vessel at the level of the second lumbar 
vertebra. Below the pancreas, the aorta is crossed by the 
third or horizontal portion of the duodenum, and, at a still 
lower level, it lies immediately behind the peritoneum on the 
posterior wall of the infra-colic compartment of the abdomen. 

In neurasthenic patients with flaccid abdominal walls, the 
pulsations of the abdominal aorta can be felt with extra- 
ordinary distinctness, but under normal conditions very firm 
deep palpation must be employed, and, even then, it is 
impossible to determine the character of the pulse. In 
aneurisms affecting the descending thoracic or the abdominal 
aorta, complete absence of pulsation in the femoral artery and 



THE GREAT VESSELS 323 

its branches is a valuable diagnostic sign when thrombosis has 
occurred. 

Tumours affecting viscera which lie in front of the abdominal 
aorta may present palpable pulsations. The viscera most com- 
monly involved are — (1) The left lobe of the liver, which lies 
in front of the descending thoracic aorta, and is separated from 
it only by the diaphragm; (2) the pylorus, which is separated 
from the abdominal aorta only by the peritoneal walls of 
the omental bursa (lesser sac) ; and (3) the pancreas, which 
crosses in front of the abdominal aorta. The pulsation in 
these cases consists of a simple, heaving, forward movement, 
and is not expansile in character. In this way, it may be dis- 
tinguished from the pulsation of an aneurism of the abdominal 
aorta, although it is only when the latter is of fairly large size 
that the expansile nature of its pulsations can be determined 
in a satisfactory manner. 

Aneurisms of the abdominal aorta usually enlarge in a 
forward direction, and the tumour which they produce can 
be palpated through the anterior abdominal wall. In some 
cases, they enlarge in a backward direction and erode the 
lumbar vertebrae, ultimately compressing the cauda equina 
(p. 40) and giving rise to paraplegia. 

The Pulmonary Artery arises from the right ventricle 
and passes upwards and backwards. At its origin it is placed 
in front of the ascending aorta, but it inclines to its left side 
and terminates below the aortic arch by dividing into right and 
left branches. At its termination it is placed behind the 
sternal end of the left second intercostal space, and is 
separated from the surface only by the thin anterior part of the 
left lung. When this part of the lung becomes retracted in 
pulmonary tuberculosis, the pulsations of the pulmonary artery 
are rendered visible in the left second interspace ; or, when 
it becomes consolidated in phthisis or pneumonia, these pulsa- 
tions may be transmitted to the surface. In either case, light 
percussion over the left half of the sternum at this level will 
demonstrate a decrease in the area of lung resonance. 



324 THE VASCULAR SYSTEM 

At its bifurcation, the pulmonary artery is attached to the 
lower surface of the aortic arch by the ligamentum arteriosum 
(p. 306). 

The Thoracic Duct is the largest lymph vessel in the 
body. It commences on the right side of the vertebral 
column in a dilatation, termed the cisterna chyli, which is 
situated in the epigastric region. From this origin the thoracic 
duct ascends into the thorax, where it lies at first behind the 
oesophagus. In the upper part of the thorax, however, it 
crosses the median plane and ascends along the left margin of 
the oesophagus in close contact with the left mediastinal pleura 
(Fig. 113). In the neck the thoracic duct lies posterior to 
the left lobe of the thyreoid gland, but, opposite the seventh 
cervical vertebra, it passes laterally and then downwards and 
terminates in the angle of union between the left internal 
jugular and subclavian veins. 

The cisterna chyli receives the lymph vessels which drain 
the alimentary canal, and it may, therefore, become infected 
in cases of intestinal tuberculosis. Some cases of miliary 
tuberculosis arise in this way. 

The Right Lymphatic Duct is a small vessel, which drains 
the lymph from the right upper limb, the right side of the head 
and neck, the right half of the thorax and its contents, and the 
upper surface of the liver. It ends in the angle of union 
between the right internal jugular and the right subclavian 
veins. 



V 

THE RESPIRATORY SYSTEM 

The Nose 

The Nasal Septum, which subdivides the nasal cavity into 
a right and a left half, is partly osseous and partly cartila- 
ginous. The vomer, which articulates with the sphenoid 
above and the hard palate below, forms the posterior part of 
the septum, and its posterior border can be seen on posterior 
rhinoscopy. Its anterior border articulates above with the 
perpendicular lamina of the ethmoid, which forms the upper 
part of the septum, and below with the septal cartilage, which 
forms the lower part of the septum (Fig. 114). 

When the growth of the individual components of the 
septum is more rapid than the growth of the septum as a 
whole, the lines of force meet one another along the articulations 
and deviation of the septum results. Osseous deviation occurs 
at the articulation between the vomer and the ethmoid, but 
cartilaginous deviation may affect any part of the septal 
cartilage. The former condition does not arise before the 
seventh year, as, at an earlier date, ossification has not pro- 
ceeded far enough to bring the two bones into contact. 

On the Lateral Wall of the Nasal Cavity, the three concha; 
(turbinated bones) project downwards and medially and sub- 
divide the cavity into an inferior, a middle and a superior 
meatus. The inferior concha forms the roof of the inferior 
meatus, and, under cover of its anterior extremity, the naso- 
lacrimal duct (p. 208) opens into the nasal cavity. The 

325 



326 



THE RESPIRATORY SYSTEM 



posterior extremity of the inferior concha extends almost to 
the choanse (posterior nares) and can therefore be inspected 
on posterior rhinoscopy. The mucous membrane, which covers 
it, is very loosely attached to the subjacent bone, and serous 
effusions into the lax submucous tissue may cause complete 




Fig. 114. — The Nasal Septum. 



a. Vomer. 

b. Perpendicular lamina of 

ethmoid. 



c. Septal cartilage. 

d. Naso-pharynx. 

e. Sphenoidal air-sinus. 



occlusion of the inferior meatus. This condition is found in 
coryza, chronic posterior hypertrophic rhinitis, etc. 

The floor of the inferior meatus, which also constitutes 
the floor of the nose, is formed by the hard palate and is 
practically horizontal. 

The middle concha forms the roof of the middle meatus and 
projects downwards and medially so as to obscure the orifices 



THE NOSE 327 

of the air-sinuses which open into it. On the side wall of 
the middle meatus there is a prominent elevation, termed the 
bulla ethmoidalis, which contains the middle ethmoidal air- 
sinuses. At the anterior extremity of the bulla, the middle 
meatus receives the infundibulum of the frontal sinus. Below, 
the bulla is limited by the hiatus semilunaris, a groove which 
receives the openings of the anterior ethmoidal air-sinuses 
anteriorly and the maxillary sinus (antrum of Highmore) 
posteriorly. The middle ethmoidal air-sinuses open into the 
middle meatus at the upper border of the bulla ethmoidalis. 

The superior concha forms the roof of the superior meatus, 
which receives the openings of the posterior group of the 
ethmoidal air-sinuses. A small recess, termed the recessus 
spheno-ethmoidalis, intervenes between the superior concha and 
the roof of the nasal cavity and receives the opening of the 
sphenoidal air-sinus. 

The air-sinuses which open into the nasal cavity are all lined 
by muco-periosteum, which is continuous with the mucous 
membrane of the nose. Owing to the proximity of the various 
orifices to one another, in the middle meatus especially, septic 
infection originating in one sinus may readily spread to involve 
the others. 

The outlines of the frontal, maxillary and sphenoidal air- 
sinuses can all be made out in X-ray photographs, and the 
condition of the first two can, to some extent, be determined 
by the process of trans-illumination. 

The Maxillary Sinus (Antrum of Highmore) is placed in the 
interior of the maxilla. It is present at birth, but does not 
begin to enlarge until about the seventh year, and after puberty 
it rapidly increases in size. The orifice by means of which it 
communicates with the middle meatus is placed high up on its 
medial wall, and, consequently, when pus collects in the sinus 
it cannot readily make its escape into the nasal cavity. 

The Frontal Sinuses are placed in the frontal bone above 
the root of the nose. They are separated from one another 
by an osseous septum, which is usually deflected to one or 



328 



THE RESPIRATORY SYSTEM 



other side of the median plane. The sinus extends backwards 
into the orbital part of the frontal bone, and lies immediately 
below the floor of the anterior part of the anterior cranial 
fossa. On this account, fractures through this part of the 




Fig. 115. — Frontal (Coronal) Section through the Skull, showing 

the nasal fossse. 



a. Inferior concha. 

b. Middle concha. 

c. Superior concha. 



d. Inferior meatus. 

e. Middle meatus. 

f. Maxillary sinus. 



g. Superior meatus. 
/;. Posterior ethmoidal 



floor of the skull open into the frontal sinus and blood and 
subdural or even cerebro-spinal fluid may be discharged from 
the nose. 

The frontal sinus does not appear much before the seventh 
year. At puberty it can be recognised in X-ray photographs, 
and it attains its maximum size between the ages of 21 and 25. 



THE NASO-PHARYNX 329 

The Naso-Pharynx 

The naso-pharynx lies behind the nasal cavity and 
constitutes the highest part of the pharynx. In front, it 
communicates with the nasal cavity through the choanae 
(posterior nares), which are each one inch long and half an 
inch wide. Below, it communicates freely with the oral part 
of the pharynx, but this communication is closed when the 
soft palate is raised (p. 97). 

The pharyngeal orifice of the auditory (Eustachian) tube is 
situated on the side wall of the naso-pharynx. Behind the 
orifice, the cartilage which supports the roof and medial wall 
of the tube forms a distinct prominence, termed the torus 
tubarius (Eustachian cushion), and this elevation forms the 
anterior wall of a small pocket of mucous membrane which 
constitutes the pharyngeal recess (fossa of Rosenmuller). 

The auditory tube passes backwards and laterally from the 
pharynx to the tympanum, and, as it is kept patent by the 
cartilage in its wall, it affords a channel for the constant 
renewal of the air in the tympanic cavity (p. 20 t). When the 
tube becomes obstructed, the air within the tympanum 
becomes absorbed and deafness results. Under certain 
conditions it is desirable to inflate the tympanic cavity, and 
this operation is conducted through the auditory tube. A 
Eustachian catheter is passed backwards along the floor of the 
inferior meatus of the nose until it impinges against the 
posterior wall of the naso-pharynx. If the instrument is then 
rotated laterally through 90°, its point will rest in the pharyngeal 
recess. It is then withdrawn slightly, and the point can be felt 
to slip over the torus tubarius and enter the pharyngeal orifice 
of the tube. 

The posterior wall of the naso-pharynx contains a small 
collection of lymphoid tissue, which is termed the pharyngeal 
tonsil. After puberty the pharyngeal tonsil rapidly atrophies, 
but before that period it may be of considerable size. In 
children this lymphoid tissue frequently proliferates and gives 



33Q THE RESPIRATORY SYSTEM 

rise to the condition of adenoids. When the adenoids are 
extensive, they fill up the nasal part of the pharynx and render 
nasal breathing impossible. In addition, the pharyngeal orifice 
of the auditory tube may become occluded, and, consequently, 
children who suffer from adenoids not only' breathe through the 
mouth but are also dull of hearing. 

As the atmospheric air passes through the nasal cavity on 
its way to the lungs, it absorbs a slight amount of moisture 
from the nasal mucous membrane and its temperature is 
slightly raised. These alterations in the character of the air 
must be brought about also when the patient breathes through 
the mouth, and, under these circumstances, the air absorbs 
moisture from the mucous membrane of the tongue, which 
becomes unpleasantly and unnaturally dry in consequence. 

The Larynx 

The larynx is kept constantly patent by its cartilaginous 
walls, and it communicates with the laryngeal part of the 
pharynx through its superior aperture. 

The thyreoid cartilage consists of two laminae which meet 
in the median plane anteriorly and form the laryngeal promin- 
ence (pomum Adami), which is subcutaneous. The cricoid 
cartilage is shaped like a signet ring. Its narrow anterior 
part can be felt through the skin i inch below the laryngeal 
prominence, and its deeper posterior part expands to fill up the 
gap which exists posteriorly between the two laminae of the 
thyreoid cartilage (Fig. 116). A small diarthrodial joint exists 
between the inferior cornu of the thyreoid and the side of the 
cricoid, and enables the cartilages to be moved, one on the 
other, by the contraction of the crico-thyreoid muscles (p. 335). 

The arytenoid cartilages, two in number, articulate with 
the upper border of the posterior part of the cricoid cartilage. 
They are pyramidal in shape and their anterior basal angles 
receive the posterior attachments of the vocal folds (true 
cords). 



THE LARYNX 



33i 



The epiglottis is a leaf-shaped cartilage and its broad, free, 
upper portion projects upwards behind the dorsum of the 




Fig. 116. — Posterior Aspect of the Cartilages of the Larynx. 
(Turner's Anatomy.) 



A. Arytenoid cartilage. 

C. Cricoid cartilage. 

CL. Corniculate cartilage. 

E. Epiglottis. 

H. Hyoid bone. 

T. Thyreoid cartilage. 

Tr. Trachea. 

e. Muscular process of arytenoid 
cartilage. 



i.e. Inferior cornu of thyreoid cartilage. 
kit. Lesser cornu of hyoid bone. 
p.c.a. Origin of crico-arytainoideus pos- 
terior. 
s.c. Superior cornu of thyreoid car- 
tilage. 
t.c. Thyreo-epiglottic ligament. 
t.h. Greater cornu of hyoid bone. 
/.//./. Lateral thyreo-hyoid ligament. 



tongue. Its narrow lower end is attached to the thyreoid 
cartilage. 

The aditus laryngis (upper aperture) is directed backwards 



332 THE RESPIRATORY SYSTEM 

and very slightly upwards towards the laryngeal part of the 
pharynx (Fig. 117). The direction of this opening must be 
borne in mind when an intubation tube is being inserted into 
the larynx. The index finger of the left hand is introduced 
into the mouth and is carried backwards over the tongue until 
the upper border of the epiglottis is reached. The intubation 
tube is then passed in with the right hand and guided along 
the left index finger. The posterior or laryngeal surface of the 
epiglottis slopes obliquely forwards and downwards, and the 
end of the tube is kept in contact with this surface until it 
enters the upper compartment of the larynx. 

The upper aperture of the larynx is bounded laterally 
by the ary-epiglottic folds (Fig. 86). They contain the 
ary-epiglottic muscles, which act as a sphincter of the opening 
during deglutition. On laryngoscopic examination, two little 
elevations, separated by a small groove, can be observed 
in the posterior part of the fold. They are produced 
by nodules of cartilage which lie in the submucous tissue. 
The more posterior nodule, which is situated on the apex 
of the arytsenoid, is termed the corniculate cartilage, and 
the more anterior the cuneiform cartilage. Occasionally, in 
tuberculous laryngitis, these elevations become abnormally 
enlarged and they may hide the interior of the larynx on 
laryngoscopic examination. 

On the lateral side of the ary-epiglottic fold there is a 
small recess, termed the recessus piriformis. The mucous 
membrane which lines it is supplied with sensation by the 
internal laryngeal nerve, and when small particles of food 
become lodged in the recess, they set up an uncontrollable fit 
of coughing (p. 97). 

The vestibule of the larynx extends from the aditus to the 
ventricular folds (false vocal cords), and, owing to the 
direction of the aditus, its anterior wall is much longer than 
its posterior wall. The anterior wall is formed by the epiglottis, 
which shows, in its lower part, a well-marked convex pro- 
minence, termed the epiglottic tubercle (cushion). 



THE LARYNX 



333 



The ventricular fold (false vocal cord) consists of a few 
muscular fibres and a weak ligamentous band, covered with 




Fig. 117.— The Interior of the Pharynx, viewed from behind, after 
removal of the posterior pharyngeal wall. 



1. Nasal septum. 

2. Inferior concha (turbinated bone). 

3. Soft palate. 

4. Uvula. 

5. Glosso-palat'me arch (anterior pillar 

of fauces). 

6. Tonsil. 



7. Pharyngo-palatine arch (posterior 

pillar of fauces). 

8. Dorsum of tongue. 

9. Epiglottis. 

10. Ary-epiglottic fold. 

11. Upper aperture of larynx. 

12. Recessus piriformis. 



13. Posterior aspect of cricoid cartilage. 

mucous membrane. Anteriorly, the two folds are attached 
side by side to the thyreoid angle, but they diverge from one 
another as they pass backwards, bounding the rima vestibuli 



334 



THE RESPIRATORY SYSTEM 



(false glottis). The ventricular folds cannot normally be 
approximated to one another, but temporary spasm is said to 
occur and to account for stammering at initial vowels. 

The ventricle of the larynx is very short ; it is bounded 




Fig. 118. — Frontal (Coronal) Section through the Larynx. 
(Turner's Anatomy.) 



E. Epiglottis. 

C. Cricoid cartilage. 

T. Thyreoid cartilage. 

Tr. Trachea. 

V. Laryngeal ventricle. 

c. Epiglottic tubercle. 

ct. Crico-thyreoid muscle. 



f. Ventricular fold (false vocal cord). 
let. Conus elasticus (crico-thyreoid 
membrane). 

p. Appendix ventriculi. 

r. Rima glottidis. 

t. Vocal fold (true vocal cord). 
ta. Thyreo-arytaenoid muscle. 



above by the ventricular folds and below by the vocal folds 
(true cords). 

The Vocal Fold consists of a strong fibrous band, termed 
the vocal ligament, which is covered laterally by the musculus 
vocalis and medially by the mucous membrane of the larynx 



THE LARYNX 335 

(Fig. 118). The mucous membrane is tightly bound down 
to the vocal ligament and, in this situation, it contains very 
few blood-vessels. On this account the vocal folds are much 
paler in colour than the surrounding mucous membrane 
under normal conditions. 

In the vestibule and ventricle of the larynx, the mucous 
membrane is very loosely bound down, except over the 
epiglottis and the vocal folds. In oedema glottidis, serum 
collects in the loose submucous tissue of the larynx and 
gravitates downwards. It cannot, however, descend over the 
vocal folds, and consequently, as it increases in amount, it 
brings the ventricular folds (false cords) and the walls of the 
cavity into contact with one another, causing complete 
obstruction to respiration. 

The vocal ligament is attached to the thyreoid angle in 
front and to the vocal process (anterior basal angle) of the 
arytenoid behind. Under favourable conditions, the vocal 
process can be seen in the posterior part of the vocal fold on 
laryngoscopic examination. 

The rima glottidis consists of an intermembranous part, 
placed between the vocal folds, and an intercartilaginous part, 
placed between the vocal processes and the bases of the 
arytenoid cartilages (Fig. 120). The differentiation into two 
parts is seen best when the glottis is widely open, as it then 
assumes a somewhat lanceolate shape. This shape is assumed 
because the arytenoid cartilages, being unable to separate 
widely from one another, undergo rotation on the cricoid so 
that the vocal processes are rotated laterally (Fig. 120). 

The muscles which act on the vocal folds may be divided 
into four groups — (a) Tensors, (b) relaxors, (c) abductors, and 
(d) adductors. 

(a) The crico-thyreoid passes backwards and upwards from 
the side of the cricoid to the thyreoid cartilage. The line of 
its pull lies in front of the crico-thyreoid joint, and conse- 
quently, when the muscle contracts, it tilts the thyreoid 
cartilage downwards and forwards. ■ As a result, the anterior 



33 6 



THE RESPIRATORY SYSTEM 



attachment of the vocal fold is carried forwards while the 
posterior attachment remains fixed, and the folds are there- 
fore rendered tense. This muscle is extrinsic in position and 
is supplied by the external laryngeal nerve (p. 97). 

(b) The vocalis and the thyreo-arytaenoid, which really 
consists of the superficial fibres of the vocalis, pass from the 
thyreoid cartilage in front to the lateral surface of the 




Fig. 119. — The Interior of the Left Half of the Larynx. The 
mucous membrane and the laryngeal muscles have been removed. 
(Turner's Anatomy.) 



A. Arytaenoid cartilage. 
C. Cricoid cartilage. 
T. Thyreoid cartilage. 
V. Laryngeal ventricle. 
a. Vocal process of arytaenoid car- 
tilage. 
f. Ventricular fold (false vocal cord). 



ic. Inferior cornu of thyreoid cartilage. 
let. Conus elasticus (crico-tbyreoid 
membrane). 
r. Thyreoid angle. 
sc. Superior cornu of thyreoid car- 
tilage. 
/. Vocal fold (true vocal cord). 



arytaenoid behind. Their contraction approximates the two 
attachments of the vocal folds, which consequently become 
relaxed. 

(c) The crico-arytaenoideus posterior arises from the 
posterior surface of the cricoid, below, and is inserted into the 
muscular process (lateral basal angle) of the arytaenoid. Its 
line of pull lies posterior to the centre of the crico-arytaenoid 
joint, and its contraction, therefore, rotates the arytaenoid so 



THE LARYNX 



337 



that its vocal process passes laterally and the vocal folds are 
abducted (Fig. 120). 

(d) The crico-arytaenoideus lateralis arises from the antero- 
lateral surface of the cricoid and passes upwards, backwards 
and laterally to reach the muscular process of the arytaenoid. 
Since its line of pull is anterior to the centre of the crico- 




Fig. 120. — Transverse Section through the Larynx at the level of 
the vocal folds (true vocal cords). (Turner's Anatomy.) 

I. The vocal folds are abducted and the rima glottidis is widely open. 
II. The vocal folds are adducted. Notice the alteration in the position of the 
arytaenoid cartilages. 



A. Arytaenoid cartilage. 
C. Cricoid cartilage. 
T. Thyreoid cartilage. 

a. Vocal process of arytaenoid cartilage. 
at. Arytasnoideus transversus. 

c. Muscular process of arytenoid 
cartilage. 



lea. Crico-arytaenoideus lateralis. 
pea. Crico-arytaenoideus posterior. 

r. Inter-cartilaginous part of rima glot- 
tidis (glottis respiratoria). 
ta. Musculus vocalis. 
v. Inter-membranous part of rima 
glottidis (glottis vocalis). 






arytaenoid joint, the vocal process is rotated in a medial 
direction (Fig. 120) when the muscle contracts. It is therefore 
an adductor of the vocal folds. 

The arytsenoideus muscle connects the two arytaenoid 
cartilages, and its contraction draws them close to one 
another, posteriorly. 

With the single exception of the crico-thyreoid, which is 
supplied by the external laryngeal nerve (p. 97), all the 
22 



338 THE RESPIRATORY SYSTEM 

muscles of the larynx are supplied by the recurrent (laryngeal) 
nerve (p. 99). 

Laryngeal Paralysis. — Bilateral paralysis of the laryngeal 
muscles is practically always accompanied by paralysis of 
other muscles, e.g., the soft palate, etc., innervated by the 
vagus. Unilateral paralysis may occur in neuritis of the vagus 
or it may be due to pressure on one of the recurrent nerves. 
In the latter case, the condition occurs more frequently on 
the left than on the right side, owing to the longer course 
which the left recurrent nerve adopts (p. 99). Both nerves 
may be affected in the neck by pleuritic thickening in apical 
phthisis, by enlargements of the thyreoid gland and by tuber- 
culous adenitis of the antero-inferior group of the deep cervical 
lymph glands. In addition, the right recurrent may be com- 
pressed at the root of the neck by aneurismal dilatation of 
the innominate artery (p. 321). On the other hand, as it passes 
upwards within the thorax, the left recurrent nerve may be 
subjected to pressure from aortic aneurisms, mediastinal 
tumours and enlargement of the para-tracheal lymph glands. 

When the recurrent (laryngeal) nerve is compressed, the 
fibres which innervate the abductor muscles are invariably the 
first to be affected. Unilateral abductor paralysis causes 
no alteration in the voice, and the condition can only be 
diagnosed by laryngoscopic examination, when it will be 
observed that the affected vocal fold does not become 
abducted during inspiration. Continuance of the pressure 
produces complete paralysis of the fold, which then assumes 
the cadaveric position. In this condition, the voice is 
rendered husky, since the breadth of the rima glottidis is 
greater than normal during phonation. The occurrence of 
pure adductor paralysis indicates that the disorder is functional 
in origin, and, as both folds are involved, the width of the 
rima glottidis is greatly increased. The condition, therefore, 
is characterised by complete aphonia. 

In the early stages of bilateral nuclear lesions, bilateral 
abductor paralysis may occur. In this case, the voice is not 



THE TRACHEA 339 

affected, but, owing to the nairowness of the rima glottidis, 
inspiration becomes laboured and difficult, and a slight degree 
of oedema glottidis may cause complete obstruction. 

Bilateral paralysis of the crico-thyreoid results in relaxation 
of the vocal folds owing to the increased tonus of the 
unopposed vocalis and thyreo-arytsenoid muscles. On laryngo- 
scopy examination, the rima glottidis is observed to become 
slightly oval in outline when the vocal folds are adducted. 
The condition never occurs alone, and it is usually accom- 
panied by other signs of vagus paralysis. 

The Trachea and Bronchi 

The Trachea begins at the lower border of the cricoid 
cartilage and extends downwards through the neck into the 
thorax. It terminates at the upper border of the fifth thoracic 
vertebra, which corresponds, in level, to the sternal angle 
(p. 294) on the anterior surface of the body and to the tip of 
the third thoracic spine on the posterior surface. 

Except at its termination, which is often displaced slightly 
to the right, the trachea lies in the median plane, and it is 
separated from the vertebral column only by the oesophagus. 
This posterior bony relation is of importance, for it renders the 
trachea liable to become narrowed when compressed in an 
antero-posterior plane. 

The isthmus of the thyreoid gland lies in front of the 
second, third and fourth rings of the trachea, and, when it 
becomes enlarged, it can exercise considerable backward 
pressure. Since the lobes of the gland are also involved, 
the trachea is gripped by the tumour and compressed against 
the vertebral column. This produces a mechanical obstruction 
to respiration, which is indicated by the characteristic "brassy" 
sound of the cough, and the condition is often aggravated by 
abductor paralysis of the vocal folds, due to pressure on the 
recurrent nerves (Fig. 50). 

Within the thorax, the trachea is crossed by the arch of the 



34° 



THE RESPIRATORY SYSTEM 



aorta (Fig. 113), and, therefore, may be subjected to pressure 
by aneurismal dilatations. It also lies behind the remains of 
the thymus gland, and may be compressed by tumours which 
have their origin in that structure. 



Epiglottis 

Hyoid bone 

Thyreo-hyoid 
membrane 



Thyreoid cartilage 
(laryngeal prominence) 



Crico-thyreoid ligament 

Cricoid cartilage "T" 



Right bronchus 
Eparterial bronchus -— 




Fig. 121. — The Larynx, Trachea and Bronchi. 



As the oesophagus is interposed between the trachea and the 
vertebral column, tumours which cause respiratory embarrass- 
ment by exercising pressure on the trachea may also give rise 
to difficulty in swallowing (Fig. 113). 

The two Bronchi, nto which the trachea bifurcates, differ 



THE PLEURAL SACS 341 

from one another both in size and direction. The right 
bronchus is the wider but shorter of the two, and it is also 
stated to be more vertical in its course (Fig. 121). Foreign 
bodies which pass into the trachea almost invariably enter the 
right bronchus. This route is selected, partly because the right 
bronchus is the wider, and partly owing to the fact that the 
bifurcation is marked in the interior of the trachea by an 
antero-posterior ridge, which is placed slightly to the left of the 
middle line of the trachea (Fig. 113). As the foreign body 
descends, in most cases it impinges on the right side of this 
ridge — even when the bifurcation is placed to the right of the 
median plane — and so it is conducted into the right bronchus. 

On this account, too, the orifice of the left bronchus may 
not be visible in bronchoscopy. It is, however, always possible 
to observe the vibrations of the left wall of the trachea, which 
are due to its intimate relationship to the aortic arch, and, if 
the point of the instrument is passed downwards in close con- 
tact with this wall, it will eventually enter the left bronchus. 

One inch from its origin from the trachea, the right bronchus 
gives off the eparterial bronchus, which proceeds to the upper 
lobe of the right lung. The corresponding branch on the left 
side arises from the bronchus at a distance of 2 inches from 
the trachea. Owing to the proximity of the point of origin of 
the right apical bronchus to the trachea, bronchial breathing 
is frequently heard on auscultation of the right apex and does 
not necessarily possess any pathological significance. 

The Pleural Cavities 

Each lung is enveloped in a serous envelope, which is 
termed the pleural sac. The pulmonary pleura is firmly 
adherent to the surfaces of the lung and covers the contiguous 
surfaces of adjoining lobes. The parietal pleura lines the 
cavity in which the lung is situated; and, for descriptive 
purposes, is subdivided into— (1) The costal pleura, which 
lines the inner surfaces of the ribs and intercostal spaces ; 



342 



THE RESPIRATORY SYSTEM 



(2) the mediastinal pleura, which covers the great vessels, etc. ; 

(3) the diaphragmatic pleura, which covers the upper surface 
of the diaphragm ; (4) the cupula pleura, which projects 
upwards into the neck in association with the apex of the 
lung. The pulmonary and parietal pleurae become continuous 
with one another at the root of the lung (Fig. 123). 

When a transverse section through the thorax above the 
level of the root of the lung is examined, it is found that there 
is no continuity between the parietal and the pulmonary 
pleurae. The costal pleura lines the inner surfaces of the ribs 




Fig. 122. — Diagram of a Transverse Section through the Thorax 
above the level of the root of the lung, showing the arrange- 
ment of the parietal and visceral layers of the pleura. 

and passes medially on the posterior surface of the sternum to 
the median plane. It there becomes continuous with the 
mediastinal pleura, which passes backwards over the great 
vessels, etc., to reach the vertebral column. At the sides of 
the bodies of the vertebras, the mediastinal pleura passes 
laterally on to the ribs (Fig. 122). 

When a section through the thorax at the level of the root 
of the lung is examined, the arrangement is found to be very 
similar in regard to the costal pleura, but, as the mediastinal 
pleura passes backwards from the sternum, it comes into con- 
tact with the pericardium. From the pericardium the pleura 
is carried laterally on the anterior surface of the root of the 



THE PLEURAL SACS 



343 



lung, and so establishes continuity with the pulmonary layer, 
which completely encircles the lung, finally returning to the 
posterior surface of the root (Fig. 123). It is then carried 
backwards to reach the vertebral column, where it becomes 
continuous with the costal layer. 

The continuity of the costal and the diaphragmatic pleurae 
can be demonstrated in frontal sections through the chest. 
From the cupula pleurae, the costal layer descends on the ribs 
to a lower level than that occupied by the lower border of the 
lung during quiet respiration. It is then reflected on to the 




Fig. 123. —Diagram of a Transverse Section through the Thorax 
at the level of the root of the lung. The continuity of the 
visceral and the parietal layers is demonstrated in the figure. 

upper surface of the diaphragm (p. 344), on which it passes 
medially till the pericardium is reached. In that situation the 
diaphragmatic layer becomes continuous with the pericardial 
portion of the mediastinal pleura, which ascends over the peri- 
cardium until it meets the lower border of the root of the lung, 
where it establishes continuity with the pulmonary pleura. At 
the upper border of the root of the lung, the pulmonary pleura 
again becomes continuous with the mediastinal pleura, which 
then ascends to the cupula pleuroe. 

Surface Marking of the Pleural Sacs. — The apex of the 
lung extends upwards into the neck for \ to 1 inch above the 
level of the clavicle. It is everywhere in contact with the 



344 THE RESPIRATORY SYSTEM 

cupula pleurae, so that the same line can be used to indicate 
both the apex of the lung and the pleural cupula on the surface 
of the body. This line commences at the junction of the 
medial and middle thirds of the clavicle, arches upwards and 
medially, and then descends to reach the sterno-clavicular joint. 
At its highest point, it lies not more than i inch above the 
clavicle. 

The line along which the costal becomes continuous with 
the mediastinal pleura is known as the costo-mediastinal line 
of reflection. Its position differs slightly on the two sides of 
the body. On the right side, it begins at the sterno-clavicular 
articulation and passes downwards and medially to the middle 
of the manubrium. From this point it descends vertically till 
it reaches the level of the sixth chondro-sternal joint, which 
corresponds to the lower limit of the mediastinal pleura on 
the anterior surface of the body. On the left side, the upper 
part of the line is similar, but, opposite the fourth chondro- 
sternal articulation, it passes laterally to the margin of the 
sternum, along which it descends to the sixth costal cartilage 
(PL II.). 

The lines of the two sides, therefore, overlap one another 
from the middle of the manubrium to the level of the fourth 
costal cartilage, but their upper and lower extremities are 
separated by small intervals. The V-shaped interval behind 
the upper part of the manubrium overlies the origins of the 
innominate and left common carotid arteries and the trachea, 
while in the lower interval the pericardium comes into direct 
apposition with the posterior surface of the sternum (p. 290). 
Light percussion over these areas gives a dull note, in conse- 
quence of these relations. 

At the lower limit of the pleural sac, the costal pleura is 
reflected on to the upper surface of the diaphragm. The 
line along which this reflection takes place is not horizontal, 
but inclines downwards as it is traced laterally (PI. II.). 
The costo-diaphragmatic line of reflection begins at the 
lower end of the costo-mediastinal line and passes down- 




■■■ 



PLATE II GENERAL VIEW OF THE ABDOMINAL AND THORACIC VISCERA. 

The lines of pleural reflection arc shown in blue. 




PLATE III— THE ABDOMINAL AND THORACIC VISCERA, FROM BEHIND. 

The lower limit of the pleural sac is indicated by the blue line. Note the relation of the pleura. 

to the spleen and to the twelfth rib. 



THE PLEURAL SACS 345 

wards and laterally behind the seventh costal cartilage and 
across the seventh intercostal space. In the 7iipple line, it 
crosses the bony extremity of the eighth rib. It continues to 
descend until it reaches the mid-axillary line, where it crosses 
the tenth rib. On the posterior surface of the body, the 
costo-diaphragmatic line of reflection ascends slightly as it 
passes medially. It crosses the eleventh and twelfth ribs and 
reaches the vertebral column opposite the lower border of the 
twelfth thoracic vertebra (PI. III.). Thus the whole of the 
lower limit of the pleural sac is placed under cover of the ribs 
except its postero-medial corner, which descends below the 
neck of the twelfth rib. The same line may be used to map 
out the costo-diaphragmatic line of reflection on both sides of 
the body. 

The lower limit of the pleural sac is placed at a much 
lower level than the lower border of the lung during quiet 
respiration, and throughout this area the costal and diaphrag- 
matic pleurae are in contact with one another. On the right 
side, the lower part of the pleural sac intervenes between the 
liver and the surface of the body, and, in consequence, it may 
be difficult to determine the presence of a small effusion in 
this situation. On the left side, this part of the pleura over- 
lies the stomach anteriorly, and, when healthy, it does not 
cause any alteration in the tympanitic note obtained on 
percussion over that viscus. Effusions of fluid, however 
small, which gravitate downwards into this part of the left 
pleural sac, can readily be detected, since they encroach on 
Traube's space (p. 244) from above, and an area of dulness to 
percussion is found to intervene between the lung resonance 
above and the stomach tympanitis below. Posteriorly, on the 
left side, the pleural sac completely overlies the spleen, which 
may be thrust downwards from under cover of the ribs by 
large pleural effusions on the left side. 

Pleuritic Effusions. — In health, there is a constant circula- 
tion of lymph through the pleural sac. The lymph enters the 
sac by a process of transudation from the neighbouring blood- 



346 THE RESPIRATORY SYSTEM 

vessels and it leaves the sac through small stomata, which are 
found in both the pulmonary and parietal pleurae, and which 
lead into small lymph vessels. Lymph, therefore, may pass 
from the pleural sac into the superficial lymph vessels of the 
lung and so reach the lymph glands at' the hilus (p. 353), 
or it may enter the lymph vessels in the thoracic wall and 
so reach the internal mammary lymph glands. When the 
pleural membrane becomes inflamed, there is an increased 
flow of lymph into the sac, and at the same time the stomata 
may become obstructed by fibrinous threads. It has been 
suggested (West) that lymph only leaves the pleural sac 
during expiration, and, therefore, large effusions, which com- 
press the lung so as to diminish its movement to a marked 
degree, remain unabsorbed. This view gains support from 
the fact that the removal of a part only of a large effusion is 
followed by re-absorption of the remainder, as it enables the 
excursions of the lung to be increased. 

When the upper limit of a large pleural effusion is 
determined by percussion, it is very rarely found to be 
horizontal. Garland and others state that the upper border 
of the dull area forms a curve which is convex upwards, the 
summit of the curve being placed at some little distance from 
the posterior median line. Sahli, however, claims that, when 
light percussion is employed, it is possible to demonstrate that 
the upper border of the dull area is a horizontal line on the 
posterior aspect of the body but that it inclines downwards 
when traced forwards round the chest. He lays stress on the 
necessity for light percussion near the posterior median line, 
as it is only when that method is employed that the observer 
can avoid the alteration in the percussion note caused by the 
healthy lung of the opposite side. The same author suggests 
that the fluid spreads upwards more easily in the posterior 
part of the pleural sac as the posterior part of the lung, being 
more voluminous, possesses a greater retractive power than the 
anterior part. 

Exploratory needling of the pleural sac is carried out 



PARACENTESIS THORACIS 347 

through an intercostal space and the needle is inserted across 
the upper border of the rib which bounds the space inferiorly 
in order to avoid the intercostal vessels and nerve, since they 
lie in relation to the lower border of the rib bounding the 
space superiorly. 

The precise site of the puncture depends on the individual 
case, but care must be taken not to insert the needle too near 
to the upper or to the lower border of the dull area. In the 
former case, the lung is penetrated, and, in the latter case, the 
diaphragm may be pierced. When possible, the needle may 
be passed in through the fifth intercostal space in the 
mid-axillary line. In well-developed subjects it may be 
difficult to identify the fifth space in that situation, but it can 
be identified by drawing a line horizontally round the body at 
the level of the fourth chondro-sternal articulation. This line 
intersects the mid-axillary line on the fifth rib or fifth 
intercostal space. 

The seventh space in the scapular line is a favourite site for 
puncture and also for the operation of Paracentesis thoracis. 
When the arm is by the side, the space is covered by the 
inferior angle of the scapula, but, when the arm is abducted or 
flexed beyond a right angle (p. 132), e.g., by placing the hand 
on the top of the head, the space becomes uncovered. This 
site possesses the advantage that, when the instrument is 
withdrawn and the arm is replaced by the side, the track of the 
needle or cannula becomes obliterated to a large extent. 

The Nerve-supply to the costal pleura is derived from 
the intercostal nerves ; the diaphragmatic pleura receives 
branches from the phrenic nerve ; the pulmonary pleura 
is supplied by the terminal branches of the pulmonary 
plexuses (p. 100). The pain of pleuritic inflammation may be 
referred to the peripheral sensory distribution of those nerves 
which have their centres in the spinal medulla at the same 
level as the nerves of supply to the pleura (p. 191). Abdominal 
pain and rigidity of the abdominal muscles are often associated 
with empyema and with the pleurisy which accompanies the 



348 THE RESPIRATORY SYSTEM 

onset of pneumonia. The skin areas and the muscles in 
question are supplied by the lower intercostal nerves, which 
are also stated to supply the costal pleura. It is, however, by 
no means certain whether the condition represents true 
viscerosensory and viscero-motor reflexes, or whether the 
intercostal nerves are directly stimulated by the inflamed 
costal pleura, with which they are in contact for a short 
distance before they pass between the external and the internal 
intercostal muscles. 

When the diaphragmatic pleura is inflamed, the terminal 
branches of the phrenic nerve are stimulated. The afferent 
impulses, therefore, pass to the fourth cervical segment of the 
spinal medulla, and they sometimes become conveyed to the 
cells which receive their impulses from the sensory branches 
of the fourth cervical nerve. When this occurs, pain is 
experienced in the area of distribution of the supra-clavicular 
nerves (Fig. 69). 

The Lungs. — The Lungs occupy the pleural sacs. They 
contain a large amount of elastic tissue, which causes them to 
contract when the pleural sacs are opened. This elasticity 
is not sufficient to expel all the air from the alveoli, and 
therefore pieces of lung tissue float in water. In a foetus 
which has not breathed the alveoli do not contain air, and 
portions of the lungs will sink when they are immersed in 
water. 

The lungs are somewhat pyramidal in shape. The rounded 
apex extends upwards and completely fills the cupula pleurae. 
The base is hollowed out to adapt itself to the shape of the 
diaphragm, on which it rests. The costal surface is separated 
from the mediastinal surface by a thin anterior and a rounded 
posterior border. 

The left lung is divided into two lobes, an upper and a lower, 
by the oblique fissure, which cuts through the lung substance as 
far as the hilus, so that there is little or no structural continuity 
between the two lobes. On this account, disease cannot spread 
directly from one lobe to the other, unless their opposed surfaces 



THE LUNGS 349 

become adherent. The right lung is divided into three lobes. 
The lower lobe is very similar to the lower lobe of the left 
lung and is limited above by the oblique fissure, but a trans- 
verse fissure cuts off a middle lobe from the antero-inferior 
part of the upper lobe. 

The apex of the lung can be mapped out on the surface of 
the body in the way described on page 344. It has already 
been shown that the costo-mediastinal lines of pleural reflection 
differ slightly on the two sides, and a similar difference, slightly 
exaggerated, exists between the anterior borders of the two 
lungs. The anterior border of the right lung corresponds 
exactly to the line of pleural reflection, but the anterior border 
of the left lung deviates widely from the line of pleural reflec- 
tion below the level of the fourth chondro-sternal articulation 
(PI. II.). As a result, there is a relatively large area of the 
pericardium which is only separated from the chest wall by 
the pleural sac. This area, together with the portion of the 
pericardium which is uncovered by pleura (p. 290), is therefore 
dull to percussion and constitutes the area of superficial cardiac 
dulness (p. 296). A small, tongue-like process of lung tissue 
projects medially in the fifth intercostal space from the notch 
in the anterior border of the left lung (Fig. 106). It some- 
times becomes consolidated in phthisis or pneumonia of the 
upper lobe, and it then gives rise to an increased area of 
cardiac pulsation. 

In quiet respiration, a definite interval exists between the 
lower border of the lung and the lower limit of the pleural 
sac. This interval increases in extent as it is traced laterally, 
and so, whereas it only amounts to ij inches in the nipple 
line, it may be as much as 3^ or even 4 inches in the 
mid-axillary line. On the posterior surface of the body, the 
interval again decreases, and, in the scapular line, it is about 
1 \ inches in depth. In forced inspiration, the lower borders 
of the lungs descend almost to the lower limit of the pleural 
sac, and areas which were dull or tympanitic to percussion 
during quiet breathing become resonant. 



350 THE RESPIRATORY SYSTEM 

Surface Marking of Lung Fissures. — The oblique fissure of 
the lung corresponds to a line drawn from the second thoracic 
spine downwards and laterally through the root of the spine of 
the scapula and across the infra-spinous fossa. It is continued 
downwards and forwards round the side of the body, and cuts 
the inferior border of the lung on the sixth costal cartilage. 
The transverse fissure may be indicated by a line drawn hori- 
zontally to the right from the middle of the sternum at the 
level of the fourth costal cartilage until it meets the oblique 
fissure in the mid-axillary line. 

When the fissures are mapped in on the surface, it is found 
that the upper lobe is most accessible from the anterior aspect 
of the body, and the lower lobe from the lateral and posterior 
aspects. The middle lobe of the right lung can only be satis- 
factorily examined from the front of the chest, as it tails off 
rapidly into the axilla. 

The relations of the fissures of the lung to the surface of 
the chest are of importance in the diagnosis of interlobar 
empyema. In this condition the area of dulness occurs on 
the line of one of the fissures. 

The Apex of the Lung projects upwards into the root of the 
neck for from a half to one inch above the clavicle, but this 
upward projection is entirely due to the obliquity of the first 
rib, which slopes downwards from the vertebral column to the 
manubrium sterni. Anteriorly, above the clavicle, the apex is 
related to the sterno-mastoid and the scalenus anterior muscles, 
and it is crossed by the first part of the subclavian artery. 
Medially, it is related to the trachea, from which it is separated 
by the carotid sheath and its contents. This relationship is of 
importance because, owing to the slope of the neck, the apex 
of the lung is usually percussed in a backward and medial 
direction, and so the lung note is altered by the tracheal 
resonance. To avoid this complication, direct backward per- 
cussion may be employed or the tracheal resonance may be 
more easily eliminated if the patient is instructed to keep the 
mouth open during the examination. 



THE LUNGS 351 

Posteriorly, the apex rests on the neck of the first rib and 
the vertebral end of the first intercostal space. Two nerves 
intervene between the rib and the pleura. They are the 
sympathetic trunk and the anterior ramus of the first thoracic 
nerve, which is passing upwards and laterally to take part in the 
formation of the brachial plexus. Either of these structures 
may be involved in the pleuritic thickening which accompanies 
phthisis and apical pneumonia. When the sympathetic is 
affected, certain vasomotor symptoms may arise, such as uni- 
lateral sweating or localised areas of flushing. Sometimes 
the fibres which ultimately supply the dilatator pupillae muscle 
are picked out, and the pupil on the affected side is markedly 
dilated. Pressure on the sympathetic trunk may account for 
the severe cerebral symptoms which occasionally complicate 
cases of apical pneumonia. Involvement of the first thoracic 
nerve is indicated by the presence of painful or hyperassthetic 
areas on the medial side of the arm. 

Lombardi's "varicose zone of alarm," which is believed to 
constitute an important aid to the early diagnosis of apical 
phthisis, depends on the close relation of the intercostal veins 
to the costal pleura. As they lie on the posterior thoracic wall, 
the intercostal veins are in direct contact with the costal pleura. 
The first intercostal vein arches forwards over the cupula pleurae 
(p. 342) to join the innominate vein. The veins which drain 
the second and third intercostal spaces unite to form the 
superior intercostal vein. On the right side, this vessel joins 
the vena azygos (major), which pours its blood into the superior 
vena cava ; on the left side, it crosses the arch of the aorta 
obliquely and terminates in the left innominate vein. All the 
intercostal vessels receive tributaries from the tissues of the 
back as well as from the intercostal muscles, etc. 

The pleural thickening which is commonly associated with 
apical phthisis may be sufficient to compress the veins which 
drain the upper spaces, and, as a result, venous varicosities 
occur on the dorsal aspect of the body near the seventh 
cervical and the upper three thoracic spines. Owing to the 



352 THE RESPIRATORY SYSTEM 

greater frequency of tuberculous disease in the right apex, the 
sign is more frequently present on the right side. 

Lombardi claims that this "varicose zone of alarm" is 
present in nearly 90 per cent, of cases of primary tuberculosis 
of the apex. 

The antero-inferior group of the deep cervical lymph glands 
lie in relation to the medial border of the scalenus anterior, and 
some members of the group are in contact with the cupula 
pleurae. These glands receive their afferents from the tonsillar 
lymph gland, amongst others, and they are, on that account, 
frequently the site of tuberculous infection. In order to 
account for the frequency of apical phthisis, the theory has 
been put forward that the lung apex is infected from the deep 
cervical lymph glands through the pleura, which first becomes 
thickened and adherent. 

The relationship which the clavicle bears to the apex of the 
lung is important, because it indicates that percussion over the 
clavicle is of little value unless precisely similar points are 
chosen on the two sides, when comparisons are being made. 
The medial inch and a half of the clavicle lies directly in front 
of the apex, from which it is separated only by the sterno-hyoid 
muscle and the innominate vein. Percussion over this part of 
the bone gives a resonant note, but its character is affected by 
the damping influence of the " plectrum." Immediately lateral 
to this portion, the clavicle is separated from the lung by the 
first rib, and the percussion note consequently alters in character. 
Beyond the first rib, the clavicle forms the anterior boundary 
of the apex of the axilla, but a resonant note is obtained on 
percussion, as the " plectrum " is no longer placed on the 
sternal extremity, which is therefore able to vibrate freely. 

The Base of the Right Lung is deeply hollowed out to 
accommodate itself to the right cupola of the diaphragm, which 
is thrust upwards by the large right lobe of the liver. The 
margins of the base form the thin lower border of the lung, 
and, in order to determine the precise downward extent of the 
right lung, very light percussion must be used. 



THE LUNGS 353 

Tropical abscess of the liver causes adhesions to form between 
the liver and the diaphragm, and it may burst through the 
diaphragm into the right pleural sac, giving rise to an 
empyaema. If the diaphragmatic pleura is adherent to the 
base of the lung, the abscess may rupture into the lung and 
be discharged by coughing. It should be remembered that 
the cough reflex is not brought about until the pus comes into 
contact with the trachea or, perhaps, with one of the larger 
bronchi. As a result, in these cases and in bronchiectasis and 
large phthisical cavities, once the cough reflex is started, it is 
continued until all the movable pus is evacuated. The 
patient then enjoys a quiescent period until a fresh accumula- 
tion reaches the larger air-passages and so induces another 
outbreak. 

The Base of the Left Lung overlies the left lobe of the liver, 
the stomach and the upper half of the spleen (p. 404). 

The mediastinal surface of the right lung is in relation, 
below and in front of the hilum, to the pericardium covering 
the right atrium. Above the hilum, it is in direct contact with 
the trachea, and this relationship helps to explain why bronchial 
breathing may be heard on ausculting a perfectly healthy right 
apex (p. 341). Above the hilum of the left lung, the trachea is 
separated from the mediastinal surface by the left subclavian 
artery, but the oesophagus, which projects slightly to the left 
side of the median plane, and the thoracic duct are often in 
direct apposition. On this account, oesophageal sounds may 
be audible at the left apex. 

The Lymph Vessels of the lung join the broncho-pulmonary 
lymph glands, which are situated in the neighbourhood of the 
hilum. Some of the efferents from these glands pass directly 
to the thoracic duct, but others join the glands around the 
bifurcation of the trachea. From the latter group, efferents 
pass upwards to the para-tracheal glands, which communicate 
freely with the inferior group of the deep cervical glands. 
This indirect connexion between the lymph vessels of the 
lung and the cervical glands may offer a channel for the 
23 



354 THE RESPIRATORY SYSTEM 

passage of infection when the latter group is the site of 
tuberculous disease (p. 352). 

The Movements of Respiration. — In the healthy adult 
male, the increase in the capacity of the thorax which is 
necessary during inspiration is obtained by the descent of the 
diaphragm, and, to a much lesser degree, by the contraction of 
the intercostal muscles. With each inspiration the fleshy 
fibres of the diaphragm, which are slightly arched, straighten 
out and pull on the central tendon. As a result of the 
straightening out of the fleshy fibres, the abdominal viscera 
are pressed downwards and the relaxed muscles of the 
abdominal wall are bulged in an outward direction. The 
central tendon descends, but only to a very slight extent, the 
amount of which may be gauged by placing the finger on the 
thyreoid prominence during deep respiration. The movement 
is transmitted from the central tendon to the fibrous peri- 
cardium, and from the fibrous pericardium to the pretracheal 
fascia. Expiration is brought about by the recoil of the 
muscular abdominal wall, which presses the abdominal viscera 
upwards against the diaphragm, causing it to resume its 
rounded dome-like shape. This variety is known as the 
abdominal or abdomino-thoracic type of respiration. 

In the adult female, the type of respiration is termed 
thoracic or thoracico-abdominal. The effect of the diaphragm 
is much less marked, and, to make up for this diminution in 
vertical depth, the transverse and antero-posterior diameters 
of the thorax are definitely increased during inspiration. This 
result is obtained by the action of the intercostal muscles, 
which raise the ribs "like pail handles." This movement in- 
creases the transverse diameter of the thorax and it also 
increases the antero-posterior diameter, as the sternal ex- 
tremities of the ribs are thrust forwards and they carry the 
sternum with them. The elevation of the eighth, ninth and 
tenth ribs, which are not attached directly to the sternum, 
causes an increase in the infra-costal angle, so that not only 
is the transverse diameter of the thorax increased, but, as more 



RESPIRATION 355 

room is provided for the abdominal viscera, the strain is taken 
off the muscular abdominal wall. As a result, although the 
actions of the diaphragm are not suspended, they are not 
indicated by the outward bulging of the abdominal wall, which 
is no longer necessary. Expiration is caused by the elastic 
recoil of the ligaments of the costo-vertebral and the chondro- 
sternal joints. The accompanying diminution of the infra- 
costal angle acts through the abdominal viscera to restore the 
diaphragm to its position of rest. 

The Cheyne-Stokes type of respiration is exhibited in the 
late stages of arterio-sclerosis, uraemia and other conditions. 
Pauses, during which respiration is completely inhibited, 
alternate with phases in which the respiratory excursions 
gradually increase to a maximum and then gradually diminish. 
Traube has suggested that, owing to the disease, the excit- 
ability of the respiratory centre is decreased. During the 
pause the blood becomes increasingly venous in character 
and eventually the centre responds to a stimulus which is 
abnormally strong. The oxidation of the blood by the 
respiratory phase weakens the stimulus so that it again becomes 
insufficient to bring about a response. 

The phenomenon known as hiccough is due to a spasmodic 
contraction of the diaphragm, accompanied by a spasmodic 
closure of the glottis. It is usually a reflex result of stimula- 
tion of the stomach, heart, peritoneum, etc. 

Paralysis of the Diaphragm. — When the diaphragm is 
paralysed, the intercostal muscles are required to produce 
a still greater increase in the transverse and antero-posterior 
diameters of the thorax, and in this they are aided by all the 
extraordinary muscles of respiration. The consequent increase 
in the capacity of the abdomen, which is due to the widening 
of the infra-costal angle, causes the anterior abdominal wall to 
collapse in the epigastric region with each inspiration. 

Respiration in Emphysema. — In emphysema the capacity 
of the thorax in the position of rest is increased to its maximum, 
so that the intercostal muscles are thrown out of action. The 



356 THE RESPIRATORY SYSTEM 

extra capacity required in inspiration is obtained by the 
diaphragm, which is aided by the accessory muscles. The 
part played by the latter group is well shown when an 
emphysematous patient has a fit of coughing. The upper 
limbs and their girdles are fixed so that those muscles which 
pass between them and the chest wall may act on the latter. 
In this way, the pectoral muscles elevate the ribs and the 
sternum, the serratus anterior elevates the ribs, and its 
digitations of origin stand out in relief on the medial wall of 
the axilla. The latissimus dorsi elevates the lower ribs and 
draws them outwards so as to increase the capacity of the 
abdomen and lessen the resistance against which the dia- 
phragm has to act. In addition to the fixation of the upper 
limbs, the head is kept fixed in the middle line to enable the 
sterno-mastoids to act on the manubrium sterni, and the 
scalene muscles to act on the upper two ribs. 

Nerve-supply of the Lungs. — The lungs receive their 
nerve-supply from the anterior and posterior pulmonary 
plexuses, which lie in relation to the root. The vagus and the 
sympathetic trunk share in the formation of both plexuses, and 
their branches accompany the vessels and bronchi into the 
lungs. It seems probable that the circular muscular coat of 
the smaller bronchi is innervated through the vagus. In 
spasmodic asthma, the circular muscle fibres become tonically 
contracted, producing profound respiratory embarrassment. 
The condition may be initiated reflexly by the stimulation of 
the gastric branches of the vagus nerves. 

It is a matter of common experience that large areas of lung 
tissue may be destroyed by disease and yet the process is 
perfectly painless. Unfortunately, no satisfactory anatomical 
explanation can be offered, for it is not sufficient to state that 
lung tissue is insensitive to pain stimuli, as it might reasonably 
be expected that the pain would be referred to the cutaneous 
distribution of the intercostal nerves, since the sympathetic 
fibres which supply the lung have their centres in the thoracic 
region of the spinal medulla. 



VI 
THE GENITO-URINARY SYSTEM 

The Kidneys 

The Kidneys are situated, for the most part, in the 
epigastric and hypochondriac regions (p. 234), but their lower 
poles extend for a short distance below the subcostal plane. 
On account of the great bulk of the right lobe of the liver, the 
right kidney lies at a somewhat lower level than the left 
kidney, but this difference in position is subject to considerable 
variation. 

As a general rule, the transpyloric plane passes through 
the hilum of the right kidney a little above its middle, 
whereas it cuts the hilum of the left kidney a little below 
its middle. 

The long axes of the kidneys are placed obliquely, so that 
the upper pole of the organ, which is almost entirely under 
cover of the costal margin, is nearer to the median plane than 
the lower pole, which projects downwards beyond the level of 
the costal margin (Fig. 124). In length the kidney measures 
about 4% inches, and it is about 2\ inches wide. The hilum 
lies ij to 2 inches from the median plane. 

When the position of the transpyloric plane has been 
determined, the information given above is sufficient to enable 
the outline of the kidney to be mapped out on the surface of 
the body. 

Relations. 1. Anteriorly. — Both kidneys are retro-peri- 
toneal and, therefore, their normal range of movement is exceed- 
as? 



358 



THE GENITO-URINARY SYSTEM 



ingly small. On the right side, the greater part of the anterior 
surface is related to the inferior aspect of the right lobe of the 
liver, but, near its lower pole, it is covered by the right 
(hepatic) flexure of the colon (Fig. 97). Enlargements of the 
right kidney may extend downwards behind the flexure and the 
ascending colon, or they may thrust the colon downwards. 
In the latter case, the dulness of the tumour to percussion is 
continuous with the hepatic dulness, and it may be a matter 




Fig. 124. — Anterior Aspect of the Trunk, showing the surface relations of 
the kidneys and ureters, the duodenum and the pancreas. 

Note. — The reference lines are the same as those shown in Fig. 87. 

of some difficulty to determine whether the tumour has arisen 
in connexion with the kidney or with the liver. In other 
cases, the colon becomes stretched across the anterior aspect 
of the tumour, so that, on percussion, a tympanitic zone is 
found crossing the dull area. 

On the left side, the kidney is crossed anteriorly by the body 
of the pancreas, which occupies a broad strip a little above the 
middle of the viscus (Fig. 125). Above the pancreas, the left 
kidney is related to the spleen and the supra-renal gland, and 
it helps in the formation of the stomach-bed (p. 245). Below 



THE KIDNEYS 



359 



the pancreas, the lateral border of the left kidney is in contact 
with the left (splenic) flexure and with the descending colon ; 
a fairly large area near the lower pole is related to the first 
coils of the jejunum. 



— " Diaphragm 



. Cardiac end 
of stomach 
Gastric sur- 

' face of spleen 

. Left supra- 
renal gland 

' Left kidney 
Splenic 
vessels 



■ — — Pancreas 




9 — — — "Left kidney 



Left colic (splenic) 
flexure 



Commencement 
of jejunum 



Fig. 125. — The relations of the Left Kidney and the Viscera which 
form the "bed" of the Stomach. 



As the left kidney is covered not only by its intimate re- 
lations, but also by the stomach and the greater omentum, 
small tumours cannot be detected by palpation. 

2. Posteriorly. — The posterior relations of the two kidneys 
are very similar. The upper third, or more, of the kidney 
rests on the posterior fibres of the diaphragm. The lower 



360 THE GENITO-URINARY SYSTEM 

half or two-thirds is in contact with three muscles ; from the 
medial to the lateral side these are the psoas major, the 
quadratus lumborum, and the transversus (Fig. 97). Between 
the kidney and the latter two muscles, the subcostal nerve 
(T. 12) and the ilio-hypogastric and ilio-inguinal nerves (L. 1) 
pass obliquely downwards and laterally, round the abdominal 
wall. Tumours of the kidney may compress these nerves and 
give rise to painful symptoms which are referred to the areas 
of their peripheral distribution, i.e. the lower part of the 
abdominal wall and the proximal parts of the thigh and the 
buttock (Fig. 74). 

Movable Kidney. — This condition must be distinguished 
from Floating Kidney, which is an extremely rare anomaly. 
In the latter case, the kidney is invaginated into the peritoneal 
cavity, and is attached to the posterior abdominal wall by 
peritoneal ligaments, whereas, in movable kidney, the viscus 
retains its normal relationship to the peritoneum, i.e. it remains 
entirely retro-peritoneal. 

The two kidneys are enclosed in a large fascial capsule, which 
also contains the aorta, the inferior vena cava, the renal vessels 
and the commencements of the two ureters (Gerota's Space). 
It is said that the capsule may extend downwards beyond the 
lower pole of the kidney, and that this condition constitutes 
an important predisposing cause of movable kidney. 

The symptoms produced by this condition are usually very 
vague and difficult to define, and it is probable that they are 
caused, for the most part, by the weight of the viscus dragging 
on the peritoneum, on the renal vessels, and on the sympathetic 
nerves, which lie on their coats. 

Palpation of the Kidney.— In highly neurotic individuals, 
the abdominal walls may be so lax that palpation of the 
anterior surfaces of the kidneys can be carried out with 
surprising ease. In such cases, the vertebral column and the 
abdominal aorta can also be felt without any difficulty. 

In order to palpate the kidney, one hand should be placed 
on the dorsal aspect of the trunk below the twelfth rib so as 



THE KIDNEYS 361 

to thrust the viscus forwards, while the other hand is placed 
on the anterior abdominal wall, just below the costal margin. 
The patient is instructed to take a deep breath, and, as the 
abdominal wall collapses with expiration, the anterior hand is 
pressed backwards and upwards under the costal margin in an 
endeavour to catch the lower pole of the kidney between the 
two hands. 

If the examination is carried out with the patient in the 
dorsal decubitus, it may not be easy to determine whether 
the kidney is movable or not. On this account the examina- 
tion should be repeated with the patient sitting up, or, if 
possible, in the erect attitude. 

Nerve-supply. — The kidney receives its nerve-supply from 
the renal plexus, which is an off-set from the aortic plexus of 
sympathetic nerves (p. 188). These nerves have their centres 
in the lower thoracic segments of the spinal medulla. 

As in the case of the liver (p. 264) and the lung (p. 356), 
pathological processes may cause serious and even fatal lesions 
of the kidney, without giving rise to any painful symptoms 
referable to the viscus. 

Tumours of the Kidney, however, may give rise to referred 
pain, not by a " viscero-sensory reflex" (p. 192), but by direct 
pressure on the subcostal, ilio-hypogastric and ilio-inguinal 
nerves (p. 360). Further, painful symptoms may be present in 
cases of movable kidney owing to traction on the sympathetic 
nerves or on the peritoneum. 

As a result of the absence of painful symptoms, for the 
diagnosis of renal conditions the physician is almost entirely 
dependent on the examination of the urine and the blood- 
pressure, and, in some cases, he may receive additional in- 
formation from radiograms. 

The Ureter. — The ureter begins at the hilum of the kidney 
and descends vertically through the abdomen at a distance of 
about i-| inches from the median plane. When perfectly 
normal, the ureter lies directly in front of the tips of the 
transverse processes of the lumbar vertebra?, from which it is 



362 THE GENITO-URINARY SYSTEM 

separated by the psoas major muscle, and it crosses the 
bifurcation of the common iliac artery at the upper aperture 
(brim) of the pelvis. It then passes downwards in front of 
the sacro-iliac joint and curves forwards a.nd medially to enter 
the supero-lateral angle of the basal, or posterior, surface of 




Fig. 126. — The Spleen and the Left Kidney and Ureter outlined on 
the Dorsal Aspect of the Body. The lower border of the left lung 
and the lower limit of the left pleural sac are also shown. 

the bladder. The termination of the ureter in the adult lies 
on a level with the second or third piece of the coccyx. 

As it descends through the abdomen, the ureter is crossed 
by the mesentery and the terminal part of the ileum, on the 
right side, and by the pelvic meso-colon, on the left side. 

Four slight constrictions, which are sufficient to delay the 
passage of a calculus, occur in the normal ureter. They are 



THE URETERS 363 

placed — (1) At its commencement; (2) opposite the transverse 
process of the third lumbar vertebra ; (3) at the upper aperture 
(brim) of the pelvis ; and (4) at its termination. The positions 
of these constrictions and the relation of the ureter to the 
transverse processes must be borne in mind in the examination 
of radiograms, as, in this way, shadows thrown by impacted 
calculi may be differentiated from shadows thrown by calcareous 
lymph glands, etc. 

The ureter receives its blood-supply from the arteries to 
which it is related as it descends from the kidney to the 
bladder. They include the renal, spermatic, common iliac 
and superior vesical arteries. The vessels conduct to the 
ureter nerves of supply from the sympathetic nervous system, 
and these nerves have their origin in the lower thoracic and 
the upper lumbar regions of the spinal medulla. 

The ureter possesses a complete coat of unstriped muscle, 
and it is believed that the passage of urine from the kidney to 
the bladder is brought about by waves of peristalsis. The 
presence of pus, a calculus or other foreign material in the 
ureter produces excessive peristaltic contractions, which are 
always associated with more or less acute pain. 

Ureteral Colic. — The Pain in ureteral colic has a charac- 
teristic distribution, which is of great help in diagnosis. When 
the wave of contraction passes along the whole length of the 
ureter, the pain commences on the dorso-lateral or dorsal 
aspect of the trunk in the lumbar region. As the peristaltic 
wave passes down, the pain passes round the trunk, but it 
descends so as to reach a lower level in front than behind, and 
it may finally radiate into the testis. 

Since the thoracic nerves supply strips of skin which are 
almost horizontal (Fig. 69), it follows that the pain is not con- 
fined to the distribution of a single nerve, but that it spreads 
from the area supplied by one nerve to that supplied by the 
nerve below. From examination of Figs. 60 and 61 it will be 
seen that the pain in ureteral colic is experienced in the regions 
supplied by the tenth, eleventh and twelfth thoracic and the 



364 THE GENITO-URINARY SYSTEM 

first lumbar nerves. The pain may also be felt in the proximal 
part of the thigh (lumbo-inguinal nerve, p. 165) and in the 
buttock (iliac branches of T. 12 and ilio-hypogastric, etc.). 
Further, the pain never affects the skin of the scrotum (S. 2, 3 
and 4, p. 184), except in its proximal part (ilio-inguinal nerve, 
L. 1, p. 163). 

The testicular pain is explained (Mackenzie) by the fact 
that the external spermatic nerve (genital branch of genito- 
crural, L. 1 and 2) supplies a few sensory twigs to the tunica 
vaginalis testis. 

The character, distribution and method of spread of the pain 
in ureteral colic combine to support the view that the pain is 
not experienced in the ureter itself. Ureteral colic, therefore, 
may be regarded as an excellent example of the " viscero- 
sensory reflex." 

At the same time it is very interesting to observe that cases 
of ureteral colic often show a well-marked " viscero-motor 
reflex" (p. 197). During the attack, the patient feels that the 
testis is drawn up towards the abdomen and local examination 
may reveal some boarding of the lower fibres of the internal 
oblique and the transversus muscles. The upward movement 
of the testis is produced by the cremaster muscle, which covers 
the testis and the spermatic cord. This muscle is really a part 
of the internal oblique, and it receives its nerve-supply from 
the external spermatic nerve (genital branch of genito-crural) 
(L. 2). The lower parts of the internal oblique and the trans- 
versus muscles are supplied by T. 10, n and 12, and L. 1. 
It is evident that the " overflow" (p. 191) of abnormal afferent 
impulses from the ureter may stimulate the cells which are 
concerned in the innervation of the internal oblique, transver- 
sus and cremaster muscles. 

Attacks of ureteral colic, however, do not always begin in the 
area of distribution of the tenth thoracic nerve. They may 
commence either one or two segments lower down. If the 
history of a case shows that attacks of pain, which originally 
began at a higher level, have more recently begun at a lower 



THE BLADDER 365 

level in the abdominal wall, the inference that the pain is due 
to an ureteral calculus, and that the calculus has travelled some 
distance down the ureter would appear to be quite justifiable. 

It is also important to remember that attacks of ureteral 
colic do not necessarily imply either complete obstruction or 
even impaction in the tube. A small calculus in the pelvis of 
the ureter may be quite sufficient to produce severe attacks 
of colic, while it may be impossible to detect its presence by 
means of radiograms. 

It has been said that the pain in renal calculus may be 
referred entirely to the opposite side of the body, but this 
statement has not been confirmed. From the fact that the 
ureter does not develop in the median plane originally, such 
an occurrence would be very difficult to understand. 

Areas of cutaneous or muscular hyperalgesia (p. 195) may 
develop in connexion with renal calculi, and they are not 
infrequently found in the areas supplied by the posterior rami 
(primary divisions) of T. 10, n and 12, and L. 1 (Fig. 60). 

The Bladder. — In the ?iewly-bom in/ant, the bladder pro- 
jects upwards from the pelvis into the abdominal cavity, and 
its anterior surface is in direct contact with the anterior 
abdominal wall. As the relative size of the pelvic cavity 
increases, it sinks downwards, and, in the adult, it is only when 
it is distended that the bladder rises up out of the pelvis. 

When it is empty, the bladder is roughly pyramidal in shape. 
The apex lies in contact with the pelvic surface of the pubic 
symphysis, and the base is directed downwards and backwards 
towards the rectum. The superior surface of the bladder 
looks upwards and backwards, and is in relation to coils of the 
small intestine or pelvic colon, while the infero-lateral surfaces 
look downwards and laterally, and are related to the pubes 
and to the floor and side walls of the pelvis. The retro-pubic 
space (of Retzius), which contains a small pad of fat, intervenes 
between the bladder and the pubic symphysis. The neck of 
the bladder, which is partly continuous with the prostate, is 
traversed by the internal orifice of the urethra. 



j66 



THE GENITO-URINARY SYSTEM 



2 , 




Fig. 127. — Median Sagittal Section of Male Pelvis, showing the relations 
of the viscera and the arrangement of the peritoneum, which is in- 
dicated in blue. The cut edges of the peritoneum are represented by 
the dark blue lines. 



I. 


Ductus (vas) deferens. 


5- 


Ejaculatory duct. 


9- 


Bulb. 


2. 


Ureter. 


6. 


Prostatic urethra. 


10. 


Urethra. 


3* 


Bladder. 


7- 


Prostate. 


11. 


Anal canal 


4- 


Seminal vesicle. 


8. 


Fossa r.avicularis. 


12. 


Rectum. 



THE BLADDER 367 

The peritoneum covers the whole of the superior surface of 
the bladder, but it does not clothe the posterior (Fig. 127) or 
the infero-lateral surfaces. Anteriorly, it is reflected from the 
apex of the bladder on to the anterior abdominal wall, and 
laterally it passes from the upper surface on to the side walls of 
the pelvis. Posteriorly, the peritoneum touches the fundus 
of the seminal vesicle (Fig. 127) and passes backwards to the 
anterior surface of the rectum. 

When the bladder fills, it rises up out of the pelvis into the 
abdomen, since it is unable to thrust the prostate downwards 
owing to the presence of the urogenital diaphragm (p. 379), 
which fills up the pubic arch. As the viscus distends, the 
superior and the infero-lateral surfaces become increased in 
size, but the posterior surface is not much altered. The peri- 
toneum which covers the superior surface of the empty bladder 
cannot stretch sufficiently to enable it to cover the whole 
surface when the viscus is enlarged. As a result, the bladder 
strips the peritoneum off the anterior abdominal wall and the 
side walls of the pelvis. In this way, the anterior part of the 
inferior aspect of the bladder is brought into contact with 
the lower part of the transversalis fascia, and no peritoneum 
intervenes between the two structures (Fig. 128). In cases, 
therefore, in which the surgeon is unable to draw off the urine 
from a distended bladder per urethram, the bladder may be 
punctured supra-pubically without fear of infecting the peri- 
toneal cavity. In some cases, however, leakage occurs into 
the retropubic space (of Retzius). 

The mucous membrane of the bladder is redundant and is 
thrown into folds when the viscus is empty. The underlying 
submucous tissue is very loosely arranged and, therefore, the 
muscular and mucous coats are not firmly adherent to one 
another. On account of this arrangement, it is possible for 
the bladder to become distended without any undue stretching 
of the mucous membrane. 

It has already been pointed out that the posterior sur- 
face of the bladder undergoes but little alteration, while the 



3 68 



THE GENITO-URINARY SYSTEM 



superior and infero-lateral surfaces are becoming increased in 
size. It is in conformity with this fact to find that the mucous 
coat on the internal aspect of the posterior surface is smooth 
and unfolded, even when the bladder is empty. This area, 
sometimes termed the internal trigone, differs from the rest of 



Peritoneum- — 




Bladder 



Seminal 
vesicle 



Prostate U ^e-=r 



Anal canal Rectum 

Fig. 128. — Median Sagittal Section through Male Pelvis, showing the 
disposition of the peritoneum when the bladder is distended. 

the bladder not only in the arrangement of its mucous coat, 
but also in its nerve-supply (vide infra). 

It is frequently important to determine whether epithelial 
cells in urinary deposits are derived from the renal tubules or 
from the urinary passages. Renal epithelial cells are usually 
cubical or spherical in shape, whereas the cells from the 
bladder are flat, and they may be round or polygonal in out- 



THE BLADDER 369 

line. But, if the cells of the deeper strata are thrown off, it 
becomes more difficult to determine their origin since they are 
provided with tail-like processes in both the kidney and the 
bladder. A marked predominance of these cells in the 
deposit is more suggestive of pyelitis than of cystitis (Sahli). 

The large cells of the pavement epithelium of the vagina or 
prepuce are frequently found in the urine. 

Development of the Bladder. — The whole of the urinary 
bladder is derived from the ventral portion of the cloaca. 

At the end of the third week of foetal life, the alimentary 
canal consists of a short tube, closed at both ends but com- 
municating freely with the yolk sac on its ventral surface 
(Fig. 1). A little caudal to this communication a short 
blind diverticulum extends from the ventral aspect of the 
gut into the body-stalk. This diverticulum is termed the 
allantois, and it plays an important part in the development of 
the bladder in some mammals. In man, however, it is very 
small, and, as will be described, it takes no part in the forma- 
tion of the bladder. 

On the cephalad aspect of the angle between the allantois 
and the hind-gut, a transverse mesodermal septum grows tail- 
wards and subdivides the cloaca into a ventral, urinary, and a 
dorsal, gut, segment (Fig. 129). The Wolffian ducts (p. 380) 
establish connexions with the lateral aspects of the cloaca, 
and when the latter becomes subdivided, they maintain their 
connexion with its ventral portion. Before the subdivision 
of the cloaca is completely effected, the ureter arises as an 
out-growth from the caudal extremity of the Wolffian duct and 
grows headwards. Later, owing to a difference in the relative 
rates of growth, the ureters come to open into the urinary 
segment of the cloaca independently of the Wolffian ducts. 

It will been seen, therefore, that the bladder arises from the 
ventral portion of the hind-gut, and that it is cut off from a 
portion of the gut-tract, which, although very small originally, 
is destined to form the whole of the large intestine. It is not 
surprising, therefore, to find that the nerve-supply of the 
24 



37o 



THE GENITO-URINARY SYSTEM 



bladder and the nerve-supply of the large intestine are 
practically identical (p. 284). 

While the partition of the cloaca is being carried out, the 
ventral wall loses its mesoderm in a part of its extent, and this 
area, in which the endoderm of the gut cbmes into apposition 
with the ectoderm of the body-wall, is termed the cloacal 
membrane. The tailward-growing septum meets the cloacal 
membrane and separates it into a ventral, genito-urinary part 
and a dorsal, anal part, which closes in the gut segment. 






1. 11. in 

Fig. 129. — The Development of the Bladder. 

In I., the cloacal membrane is just beginning to form. In II., it is very extensive, and 
the cloaca is being divided into ventral and dorsal portions. In III., the sub-division 
of the cloaca is complete and the uro-genital and anal membranes have ruptured. 



1. Hind-gut. 

2. Allantois. 

3. Cloacal membrane. 

4. Cloaca. 



5. Genital tubercle. 

6. Ventral, urinary, part of 

cloaca. 

7. Dorsal, gut, part of cloaca. 



8. Perineal orifice of uro- 

genital sinus. 

9. Anal orifice. 



Under normal conditions these membranes break down 
during the third month of fcetal life. The anal membrane 
has already been considered (p. 287). The genito-urinary 
membrane breaks down caudal to the genital tubercle, which 
consists of a heaping up of the surface ectoderm at the 
cephalic extremity of the membrane (Fig. 129). This 
perineal orifice persists in the female, but it undergoes certain 
changes in the male. 

Two elevations, termed the labio-scrotal folds, form one on 
each side of the genital tubercle and grow tailwards. In the 



THE BLADDER 371 

female they remain separated by the pudendal cleft and form the 
labia majora. In the male, they fuse with one another, caudal 
to the genital tubercle, and they thus roof in the perineal orifice 
of the bladder, which then opens on the caudal surface of the 
tubercle. The genital tubercle forms the penis and the 
urethral orifice is situated at the base of the glans, which 
becomes canaliculised at a slightly later period. The urethra 
thus acquires its normal external orifice, and the opening at 
the base of the glans disappears. 

Congenital Anomalies of the bladder and urethra are by 
no means uncommon. In the condition of epispadias the 
urethra opens on the dorsal aspect of the penis, which is more 
or less malformed. A similar deformity may occur in the 
female, the urethra opening on the dorsal aspect of the clitoris. 
This condition is brought about by rupture of the genito- 
urinary membrane on the cephalic instead of on the caudal 
aspect of the genital tubercle. 

Hypospadias, which is the normal condition in the female, 
may occur abnormally in the male. The anomaly varies 
greatly in degree. (1) The orifice at the base of the glans 
may persist — the commonest and simplest form. (2) The 
two halves of the scrotum may fail to fuse in the median 
plane ; either partially or (3) completely, in which case the 
perineal orifice of the urethra persists. 

Extroversion of the Bladder is merely an exaggeration of 
the condition of epispadias. 

The Nerve-supply of the Bladder is derived mainly 
from the hypogastric sympathetic plexus (p. 188), and the 
fibres have their lower centres in the eleventh and twelfth 
thoracic, the first lumbar, and the second and third sacral 
segments of the spinal medulla. Reference to the description 
of the nerve-supply of the large intestine will show that it is 
also innervated from the same segments. 

Vesical Pain. — Referred pains in connexion with the 
bladder are not uncommon, and their distribution suggests the 
probability that, whereas the internal trigone is supplied by 



;72 



THE GENITO-URINARY SYSTEM 



the sacral segments, the rest of the bladder is supplied from 
the lower thoracic and upper lumbar segments of the spinal 
medulla. For example, when the bladder becomes greatly 
distended, the internal trigone is little affected/but the other 







\P)wto by Alinari. 
Fig. 130. — The Nerve-supply of the Anterior Aspect of the Trunk. 



parts of the viscus become more or less stretched. This con- 
dition gives rise to referred pain, which is experienced over the 
lower part of the anterior abdominal wall, i.e., in the areas 
supplied by the terminal branches of the anterior rami 
(primary divisions) of the eleventh and twelfth thoracic and 



MICTURITION 373 

the first lumbar nerves (Fig. 130). On the other hand, when 
the mucous membrane of the internal trigone is irritated by 
the presence of a vesical calculus, referred pain is experi- 
enced in the perineum and along the penis, i.e., in the areas 
supplied by the terminal branches of the second and third 
sacral nerves (Fig. 130). 

The Act of Micturition is partly automatic and partly 
under voluntary control. As the bladder fills, the inhibitory 
nerves are stimulated and the muscular walls become relaxed, 
with the exception of the circular fibres which surround the 
internal urethral orifice, and they, on the other hand, become 
tonically contracted. As the intra-vesical pressure increases, 
the afferent nerves of the bladder are stimulated and the 
micturition reflex is brought into play. This reflex is con- 
trolled by a centre in the hypogastric sympathetic plexus 
(p. 188). So long as the connexions between this centre and 
the cerebral cortex are intact, the subject becomes conscious 
of the desire to micturate, and he is able to control it. If, 
however, the connexions are interfered with, as in fracture 
dislocations in the mid or upper thoracic region, the act of 
micturition becomes entirely automatic (p. 48). 

A lesion of the lower thoracic or upper lumbar region of 
the spinal medulla may lead to paresis of the bladder. In 
this condition the viscus is able to distend, but is unable to 
evacuate its contents. Unless the possibility of this con- 
dition is recognised, the bladder will become enormously 
distended, and, eventually, the urine will commence to dribble 
away. As the nervous mechanism regains control after a short 
time in some cases, it is important that the damage caused by 
overstretching of the walls of the bladder should be anticipated 
and prevented by the periodical passage of a catheter. 

Frequency of micturition, with or without straining efforts, is 
a common symptom in disturbances of the urinary tract. It is 
necessary to remember, however, that this symptom is the out- 
come of the presence of a "focus of irritation " (p. 195) in the 
lumbar region of the spinal medulla, because, although such 



374 THE GENITO-URINARY SYSTEM 

a focus is usually set up by pathological conditions of the 
bladder, it may also arise as the result of abnormal afferent 
impulses from the large intestine. Frequency of micturition 
is a frequent accompaniment of irritative conditions of the 
rectum, and it is not uncommon in connexion with appendicitis 
(p. 277). 

It is interesting to observe that cases of retention of urine 
are occasionally mistaken for appendicitis, and that the passage 
of a catheter is sufficient to remove the symptoms. 

The Prostate lies between the neck of the bladder and 
the pelvic surface of the urogenital diaphragm (p. 379) and is 
traversed by the first part of the urethra. It consists of 
non-striped muscle fibres, which are continuous with the 
corresponding coat of the bladder, fibrous tissue and glandular 
tissue. On each side the prostate is related to the levator 
prostatse (the anterior portion of the levator ani, p. 184), and, 
posteriorly, it is only separated from the anterior aspect of the 
rectal ampulla by some loose connective tissue. The posterior 
aspect and the adjoining parts of the lateral surfaces of the 
prostate can be palpated on rectal examination. 

Prostatic hypertrophy may be due to overgrowth of all or 
any of its constituent tissues. When non-malignant, the 
condition is only important in so far as it obstructs the outflow 
of urine from the bladder. In this respect, enlargement of 
the, so-called, middle lobe of the prostate is of great importance. 
The portion of the organ which gets this name is situated 
between the ejaculatory ducts and the urethra, i.e., in the 
upper and posterior part of the prostate (Fig. 127). In some 
subjects, it projects upwards and forms a small elevation in 
the internal trigone of the bladder, immediately behind the 
internal orifice of the urethra. When the middle lobe becomes 
hypertrophied, the normal elevation becomes larger and is 
crushed forwards over the internal orifice when the bladder 
contracts. In these cases, therefore, the patient fails to 
empty his bladder completely at each micturition. The 
urine which is. left behind is termed the "residual urine," and 



THE TESTIS 375 

it tends to collect in a small, but gradually increasing, pocket 
behind the enlarged portion of the gland. As the residual 
urine is very apt to undergo fermentative changes and to set 
up cystitis, it is a matter of great importance that the patient 
should make every effort to empty the bladder completely, 
the expedient of passing urine "on hands and knees" being 
very useful in this respect in some cases. 

The Testis is oval in shape and lies in the scrotum with 
its upper pole tilted slightly forwards. The two glands do 
not lie at the same level, and the left one is usually the lower. 
The nerve-supply of the testis is derived from the sympathetic 
system (L. i and 2 ? ) and reaches the gland by accompanying 
the internal spermatic artery. Mackenzie states that a branch 
of the external spermatic nerve (genital branch of genito- 
crural) supplies the visceral coat of the tunica vaginalis, 
which is a portion of the peritoneum that has become shut 
off from the general peritoneal lining of the abdomen. 
Referred pain felt in the testis in cases of renal colic is 
therefore experienced in the terminal fibres of the external 
spermatic nerve. 

The testis receives its blood-supply from the abdominal 
aorta through the internal spermatic artery, which reaches its 
destination by passing through the inguinal canal as one of 
the constituents of the spermatic cord. Numerous veins 
emerge from the testis and ascend along the cord to gain the 
interior of the abdomen. They constitute the pampiniform 
plexus, and, owing partly to their dependent position and 
partly to the absence of valves, they are liable to become 
varicose. The condition, however, almost invariably occurs 
on the left side, and no really satisfactory explanation has yet 
been offered. 

The efferent ducts of the testis emerge from its upper 
pole and pass directly into the caput (globus major) of the 
epididymis, where they unite to form a much convoluted 
tube. 

The Epididymis is an elongated structure, which is closely 



376 



THE GENITO-URINARY SYSTEM 



applied to the posterior border of the testis. The caput 
(globus major) lies on the upper pole of the testis and is 
connected to it by the efferent ducts. The body and the 
tail are attached to the testis only by connective tissue, and, 
in rare cases, this attachment may fail, but' the condition does 




Fig. 131. — Diagram of the Male Reproductive Organs. 
(Turner's Anatomy.) 



B. Bladder. 
P. Prostate. 
/;. Urethral bulb. 
c. Crus penis. 
ur. Urethra. 
cc. Corpus cavernosum 
penis. 



cs. Corpus cavernosum 
urethras. 

g. Glans penis. 

/. Prepuce. 

T. Testis. 
ve. Vasa efferentia. 
in. Caput of epididymis. 



va. Vas aberrans. 
mi. Tail of epididy- 
mis. 
vd. Ductus (vas) de- 
ferens. 
vs. Seminal vesicle. 
«. Prostatic utricle. 



not necessitate any abnormality in either structure. The 
coiled tube of the epididymis emerges from the medial aspect 
of the tail and ascends along the posterior border of the 
testis, on the medial side of the epididymis. At the upper 
pole of the testis, this duct, which is termed the ductus (vas) 
deferens, enters the spermatic cord and ascends to the 
subcutaneous inguinal (ext. abdom.) ring. In this part of its 



THE SPERMATIC CORD 377 

course, the spermatic cord is covered only by skin and 
superficial fascia and it can be grasped between the fingers 
and thumb. When this is done, no difficulty is experienced 
in identifying the ductus deferens, for since its muscular 
wall is very thick in proportion to its lumen, it feels like a 
solid piece of whip-cord. 

The subcutaneous inguinal (external abdominal) ring is a 
gap in the aponeurosis of the external oblique muscle (p. 162), 
situated above the lateral part of the pubic crest and the medial 
extremity of the inguinal ligament (of Poupart). It is triangular 
in outline, the apex being directed upwards and laterally. The 
size of the ring can be determined by the finger. In order that 
this may be done, the skin of the scrotum must be invaginated 
and the finger carried upwards over the front of the pubis. 
The pubic crest and tubercle having been identified, the 
finger must then be pressed backwards, when its tip will be 
found to engage in the subcutaneous inguinal ring. If, after 
the pubic crest is reached, the finger is carried upwards, it 
lies between the superficial fascia of the abdominal wall and 
the external oblique aponeurosis and it can be moved about 
freely in this stratum. 

After entering the subcutaneous inguinal ring, the spermatic 
cord passes laterally and slightly upwards and backwards in 
the inguinal canal till it reaches the abdominal inguinal (int. 
abd.) ring, where its constituent parts separate. The ductus 
(vas) deferens descends into the pelvis, crosses the terminal 
part of the ureter and then descends on the posterior aspect 
of the bladder, in contact with the duct of the opposite side. 
As it lies in this situation, it has the seminal vesicle to its 
lateral side. The vesicle is a sacculated diverticulum, which not 
only acts as a reservoir for the seminal fluid but also possesses 
a secretion of its own. Inferiorly the vesicle narrows to form a 
duct, which opens into the ductus deferens at the upper border 
of the prostate (Fig. 132). In this way, the ejaculatory duct 
is formed, and it passes downwards and forwards through the 
prostate to open into the prostatic part of the urethra. 



378 



THE GENITO-URINARY SYSTEM 



Both the ductus deferentes and the seminal vesicles can be 
palpated through the anterior wall of the rectal ampulla (p. 
283), but it is only when they are thickened by inflammatory 
processes that they can be made out with certainty. 

Very little is known about the nerve-supply of these 
structures, but, since the ureter arises from the distal portion 
of the Wolffian duct (p. 380), the nerve-supply of the ductus 
deferens, which represents the persistent Wolffian duct (p. 
380), must, in its terminal part at least, correspond to the 

Cut edge of peritoneum 

j 

-Ureter 

- Ductus deferens 



ijf - Seminal vesicle 




/ Infero-lateral 

16- — — "" surface of bladder 



Ejaculatory duct 



- Prostate 



Fig. 132. — The Urinary Bladder and the Prostate, viewed from behind. 



nerve-supply of the ureter. The rest of the Wolffian duct 
arises in the abdomen, and it would appear likely that several 
segments above the first lumbar take part in the innerva- 
tion of the ductus deferens. Referred pains in connexion with 
these structures have not yet been sufficiently studied. 

The Urethra begins at the internal orifice at the neck 
of the bladder and passes downwards and forwards through 
the prostate. At the apex of the prostate, it pierces the uro- 
genital diaphragm and then enters the bulb of the penis, in 
which it passes upwards and forwards to the corpus cavernosum 



THE URETHRA 379 

urethral (corpus spongiosum). This part of the tube is fixed 
in position, but the cavernous (spongy) part of the urethra, 
situated within the body of the penis, is freely movable. It 
is in the most dependent part of the urethra that organisms 
tend to settle down, and consequently gonorrheal stricture 
commonly occurs within the bulb of the penis. 

The prostatic portion of the urethra (Fig. 127) is the 
most dilatable part of the canal. A longitudinal elevation, 
termed the urethral crest, is present on its dorsal wall (or 
floor) and the groove on each side of it receives the openings 
of the prostatic ducts. Gonorrhceal inflammation may pass 
backwards into the prostatic urethra, and, if it affects the 
prostatic duct, a troublesome chronic gleet will supervene. 
At the anterior end of the urethral crest, there is a small 
opening in the floor of the urethra. It leads into a short, 
blind diverticulum, termed the prostatic utricle (sinus pocularis), 
which is all that exists in the male as the homologue of the 
uterus and vagina (Fig. 131). At or near the orifice of the 
prostatic utricle, the ejaculatory ducts open into the prostatic 
urethra. They may be infected in posterior urethritis and lead 
to inflammation of the seminal vesicles or of the epididymis. 

The membranous part of the urethra lies between the two 
layers of fascia of the urogenital diaphragm (the two layers of 
the triangular ligament). It is only half an inch long (Fig. 
127), but it is of importance because a false passage may be 
made with a bougie, in endeavouring to pass the instrument 
from the cavernous (spongy) part into the membranous 
urethra. 

The cavernous (spongy) portion of the urethra is 6 to 8 
inches long. It is narrowest at the external orifice on the 
surface of the glans and is widest within the substance of the 
glans. A vesical calculus may be passed along the urethra 
and be unable to pass through its external orifice. 

The deep surface of the prepuce consists of modified skin 
and the surface of the glans possesses a similar covering. 
Normally, after the development of the prepuce is complete, 



380 THE GENITO-URINARY SYSTEM 

the skin covering these two surfaces only becomes continuous 
at the base of the glans and at the frenulum. It often happens, 
however, that the two opposed surfaces remain adherent to 
one another in some areas. Such adhesions are capable of 
producing reflex symptoms, which may vary from enuresis to 
symptoms closely resembling vesical calculus. The areas of 
skin involved are supplied by the dorsal nerves of the penis 
(S. 2, 3 and 4) (p. 184), and it would appear that the adhesions 
affect their terminal fibres in some way so as to set up a 
"focus of irritation" (p. 195) within the mid-sacral region of 
the spinal medulla. This portion of the spinal medulla is 
accustomed to receive impulses from the internal trigone of 
the bladder (p. 368), including the ordinary impulses which 
are interpreted in the cortex as a desire to micturate. The 
establishment of a " focus of irritation " in this situation will, 
if sufficiently strong, produce symptoms identical with those 
in which the internal trigone is irritated by the presence of a 
vesical calculus. Why such simple adhesions should be 
capable of causing such violent reflexes has not yet been 
explained satisfactorily. Simple division of the adhesions 
removes all the symptoms. 

Development of the Epididymis, Ductus Deferens 
and Testis. — The development of these three structures is 
intimately associated with the presence of the transitory 
Wolffian body during early foetal life. 

The Wolffian Body, or primitive kidney, is an elongated 
gland which lies on the posterior abdominal wall. It possesses 
a longitudinal duct which opens, at its caudal extremity, into 
the ventral portion of the cloaca (p. 369). 

The reproductive gland, which at first possesses no sexual 
characteristics, lies on the ventral aspect of the Wolffian body. 
In the male, it becomes differentiated into the testis, and its 
tubules gain a connexion with the Wolffian Duct, as the 
Wolffian body atrophies. This connexion persists and the 
cephalad portion of the duct develops into the epididymis, 
while its caudal portion becomes the ductus deferens. 



THE FEMALE PELVIS 381 

The Miillerian ducts, which take an important part in the 
formation of the reproductive organs in the female (p. 397), 

J ^--Appendix testis (Miillerian duct) 

Epididymis ^i-CM "1 ~ Test!s 

(Wolffian duct) 



Ductus deferens _ _- ■ 
(Wolffian duct) 



Ejaculatory duct (Wolffian duct)' 




Seminal vesicle (Wolffian duct) 

Prostatic utricle 



(Miillerian duct) 



Fig. 133.— The Development of the Male Reproductive Organs. 
The dotted lines indicate the main part of the Miillerian duct, which entirely disappears. 

disappear almost entirely in the male. Their fused caudal 
extremities form the prostatic utricle (sinus pocularis, p. 379), 
while their cephalad extremities are represented by small 
appendages, which are situated on the upper poles of the testes. 

The Female Pelvis and Reproductive Organs 

The Osseous Pelvis of the female is constructed so as to 
provide a roomy cavity and wide upper and lower apertures 
for the passage of the foetal head. The female pelvis differs 
from the male pelvis in many ways, but the most important 
difference is traceable to the sacrum, which is much wider in 
proportion to its length. As a result, the cavity of the female 
pelvis may be described as a " short section of a long cone," 



382 THE GENITO-URINARY SYSTEM 

whereas the male pelvis represents a " long section of a short 
cone." 

Congenital anomalies of the sacrum which influence the 
size of the cavity or the apertures are not of frequent 
occurrence. Occasionally the ala of the 'sacrum may fail to 
develop, and this deficiency causes a marked diminution in 
the oblique diameter of the pelvis (Nccgele pelvis). A still 
rarer anomaly is the congenital absence of both aire (Roberts' 
pelvis). 

At the lumbo-sacral articulation the convexity of the lumbar 
curve becomes continuous with the concavity of the sacral 
curve at the sacral promontory (Fig. 134). In this situation 
the vertebral column may be dislocated forwards on the 
sacrum, as the result of an injury, the real significance of 
which is often overlooked at the time of the accident owing to 
the absence of nervous symptoms. As a result of this injury, 
the antero-posterior diameter of the pelvic inlet is considerably 
diminished, and the foetal head is prevented from entering the 
pelvis (Spondylolisthetic pelvis). 

Other bony differences distinguish the female from the male 
pelvis. The pubic crests are longer, and on this account the 
acetabula have a more lateral inclination. The greater 
trochanters, therefore, are more widely separated, giving the 
subject an appearance of increased breadth. The medial 
slope of the long axis of the femur is greater in the female, 
and this difference constitutes a slight, but normal, degree of 
knock-knee. 

The available space within the pelvic cavity is increased in 
the female by the larger size of the pubic arch and of the 
greater and lesser sciatic foramina. In addition, the spines 
and tuberosities of the ischium, which tend to encroach on 
the cavity in the male, are somewhat out-turned in the 
female. 

The following tables, which are taken from Cunningham's 
Text-Book of Anatomy, indicate the measurements of the 
average female pelvis. 



THE FEMALE PELVIS 



383 



Pelvis Major (False Pelvis) 

Maximum distance between iliac crests . 
Distance between antero-superior iliac spines . 
Distance between fifth lumbar spine and the front of 
the pubic symphysis (the external conjugate) 



1 of inches 
9* j) 



Pelvis Minor (True 


Pelvis) 




Anlero-posterior diameter 

Oblique diameter . 
Transverse diameter 


Upper 
Aperture. 


Cavity. 


Lower 
Aperture. 


4s inches 

5 inches 
5j inches 


4| (min.) to 5 
inches (max.) 

4g (min.) to 4I 
inches (max.) 


4! inches 

4^ inches 
4§ inches 



These measurements apply to the bony pelvis. The measure- 
ments of the pelvis major, however, can be readily carried out 
on the living subject, and the relation between the interspinous 
and the intercristal diameters sometimes gives a good indica- 
tion as to the condition of the pelvis minor. The external 
conjugate can also be obtained, and, within wide limits, it helps 
to determine the antero-posterior diameter of the upper aper- 
ture (brim). When the measurement exceeds 8| inches in the 
living subject, there is no shortening of the latter diameter ; 
on the other hand, when the measurement falls below 6h inches, 
the antero-posterior diameter of the upper aperture is definitely 
diminished. 

When the external conjugate falls between these limits, 
other measurements are required. Of these the most useful 
is the diagonal conjugate. It represents the distance between 
the inferior aspect of the pubic symphysis and the sacral pro- 
montory, and it can be determined on vaginal examination. 
Under normal conditions, the diagonal conjugate is rather 



384 



THE GENITO-URINARY SYSTEM 




Fig. 134.— Median Sagittal Section through the Female Pelvis, showing the 
relations of the viscera and the arrangement of the peritoneum, which 
is indicated in blue. The cut edges of the peritoneum are represented 
by the dark blue lines. 



1. Caecum. 

2. Round ligament of 

uterus. 

3. Ovary. 



4. Uterine (Fallopian) tube. 

5. Uterus. 

6. Cervix uteri. 

7. Bladder. 



8. Urethra. 

9. Vagina. 

10. Rectum. 

11. Anal canal. 



more than half an inch greater than the antero-posterior 
diameter of the upper aperture. 

The floor of the pelvis is formed by the coccygei and the 



THE FEMALE PELVIS 385 

levatores ani (p. 184), which separate the pelvis proper from 
the perineum. In the female, the levator ani supports the 
lateral walls of the vagina in much the same way as it supports 
the prostate in the male. 

Peritoneum of Female Pelvis. — The arrangement of the 
pelvic peritoneum is of great importance. When a sagittal 
median section is examined (Fig. 134) it is found that the 
peritoneum, after covering the upper two-thirds of the rectum, 
is reflected forwards and comes into relation with the posterior 
wall of the vagina, which it clothes in its upper fifth or quarter. 
Ascending over the posterior aspect of the uterus, the peri- 

_ . Uterine tube 
Ovarian artery 
_ Ovary 

.Posterior layer of 
broad ligament 

Uterine artery 



Fig. 135. — Diagram of a Sagittal Section through the Broad Ligament 
of the Uterus and its contents. The round ligament is shown in 
contact with the anterior layer of the broad ligament. 

toneum is carried forwards on the fundus and then downwards 
on the anterior aspect. In this position, however, its relation 
to the uterus is much less complete than on the posterior 
aspect, for it passes forwards on to the superior surface of the 
bladder before reaching the cervix (Fig. 134). 

It will be seen that there are two well-marked peritoneal 
fossae in the female pelvis, which lie, respectively, in front of 
and behind the uterus. These fossae are normally occupied 
by coils of small intestine or of pelvic colon, but they may 
lodsre tumours in connexion with various viscera. 

The uterine (Fallopian) tubes extend laterally from the 
supero-lateral angles of the body of the uterus, and they are 
related to a fold of peritoneum, termed the Broad Ligament of 

2 5 




3 86 THE GENITO-URINARY SYSTEM 

the Uterus. This arrangement is well seen in Figs. 135 and 
136. Fig. 135 represents a sagittal section made immediately 
to the lateral side of the uterus. It will be seen that the 
peritoneum on the posterior wall of the pelvis passes forwards 
on the pelvic floor and then ascends to reach the uterine tube, 
in this way forming the posterior layer of the broad ligament, 
which is continuous medially with the layer covering the 
posterior surface of the uterus. After covering the uterine 
tube, the peritoneum descends anteriorly to the pelvic floor 
forming the anterior layer of the broad ligament, which is 
similarly continuous with the peritoneum on the front of the 
uterus. In Fig. 136, the pelvis has been cut transversely, and 







mmtmz 



Fig. 136. — Diagram of a Transverse Section through the Uterus 
and the Broad Ligaments, near the lower borders of the latter, 
showing the relation of the uterine artery to the ureter. 

the relation of the peritoneum covering the uterus to the 
broad ligament is well shown. When the two layers of the 
broad ligament are traced laterally, they separate from one 
another and pass forwards and backwards, respectively, on the 
side wall of the pelvis. It is at this point of separation that 
the uterine and ovarian vessels enter and leave the broad 
ligament. 

Certain portions of the broad ligament receive special names. 
(a) The part immediately below the uterine (Fallopian) tube is 
termed the mesosalpinx, (d) The small fold which connects 
the ovary to the posterior aspect of the broad ligament is 
termed the mesovarium. (c) The suspensory ligament of the 
ovary is that part of the broad ligament which extends 
between the lateral aspect of the ovary and the side wall of 



THE VAGINA 387 

the pelvis (Fig. 137). It contains the ovarian vessels and 
nerves, etc. 

The Vagina. — The vagina extends upwards and backwards 
from the genital cleft in the perineum. It is about 3 inches 
long and, at its upper end, it is attached to the cervix uteri. 
This attachment is placed at a higher level on the posterior 
aspect than on the anterior aspect of the cervix. As a result, 
the posterior wall of the vagina is slightly longer than the 
anterior wall, and the recess which is caused by the downward 
projection of the cervix is deeper behind than in front. This 
recess is termed the fornix vaginae. The anteror wall of the 
vagina is related to the urethra and the posterior surface of 
the bladder, and this close relationship explains the occurrence 
of urethro-vaginal and vesico-vaginal fistula and vesico-celes. 

Posteriorly, the vagina is related to the perineal body, a 
fibro-muscular node which separates it from the anal canal. 
At a slightly higher level, the vagina is closely related to the 
rectum, from which it is only separated by the visceral pelvic 
fascia. The uppermost part of the posterior wall of the vagina 
is separated from the rectum by the lowest part of the utero- 
rectal peritoneal fossa (Fig. 134). 

A Vaginal Examination gives valuable information about 
the condition of the pelvic viscera and the contents of the 
pelvic peritoneal fossse. The orifice of the vagina is guarded 
by the labia majora, two folds of skin which form the lateral 
boundaries of the pudendal cleft. When they have been 
separated, two smaller folds, termed the labia minora, are 
exposed, and care must be taken not to invert these folds into 
the vagina when the fingers are introduced. Stretching of 
the inverted labia minora gives rise to acute pain and dis- 
comfort. The presence of calculi or other foreign bodies in 
the urethra or the bladder can be determined by compressing 
the anterior wall of the vagina against the pubes. In malignant 
disease of the cervix, palpation of the anterior fornix deter- 
mines the condition of the bladder, and the possibility of 
successful surgical interference depends on the freedom of the 



388 THE GENITO-URINARY SYSTEM 

bladder from the disease. While the fingers are in the anterior 
fornix, bi-manual examination will determine whether or not 
the uterus is in its normal anteflexed and anteverted position. 

Through the posterior wall of the vagina, the condition of 
the rectum can be investigated and a higher level can usually 
be reached than is possible on examination per rectum. Both 
methods, therefore, should be employed before a diagnosis is 
arrived at. In addition, palpation of the posterior fornix 
enables the observer to determine the presence of tumours, 
exudates, etc., in the utero-rectal fossa. 

During the examination, the condition of the cervix uteri 
and the character of the external os should be noted. In the 
virgin, the external os feels like a small dimple, but it is an 
irregularly transverse slit in those who have borne children. 

The walls of the vagina are lined by squamous epithelium, 
and the same tissue covers the vaginal portion of the cervix. 
At the external os, the squamous epithelium merges into the 
columnar ciliated epithelium of the cervical canal. It follows 
that malignant disease of the vagina and outer surface of the 
cervix is of the nature of a squamous-celled epithelioma, which 
spreads by the lymph stream and does not tend to spread 
upwards to involve the uterus. 

The lymph vessels from the lower portion of the vagina 
terminate in the medial group of the subinguinal lymph glands, 
which lie below the medial end of the inguinal ligament (of 
Poupart) on the fascia lata of the thigh. 

From the upper part of the vagina, the lymph vessels pass 
to the external iliac and the hypogastric lymph glands, which 
lie in relation with the external iliac and the hypogastric 
(internal iliac) arteries. 

Perineal Laceration. — During the delivery of the foetal 
head or shoulders, the vaginal wall may be ruptured. The 
tear invariably involves the lower part of the posterior vaginal 
wall, since this is the area which is put most on the stretch. 
The skin of the perineum immediately behind the vaginal 
opening is torn and the perineal body is involved, in varying 



THE VAGINA 389 

degree according to the extent of the rupture. In a severe 
case the tear may pass backwards through the perineal body, 
and both the internal and external sphincters may be divided, 
as well as some fibres of the levator ani. When, and only 
when, the internal sphincter is ruptured, incontinence of 
feces results. 

The condition is as important in view of its remote conse- 
quences as it is in view of the possibility of immediate sepsis. 
Injury to the levator ani muscle lessens the support normally 
provided for the wall of the vagina and, during defecation, the 
anterior wall of the rectum is thrust forwards, bulging into the 
posterior vaginal wall and carrying it downwards and forwards. 
Such a bulging may appear at the vulva and is then known as 
a recto-cele. Following this condition, a strain is thrown on 
the anterior wall of the vagina, which also prolapses through 
the vulva, sometimes carrying a part of the bladder with it — a 
cysto-cele. As a result, traction is exerted in a downward 
direction on the uterus, and the utero-sacral ligaments (p. 391) 
become lengthened. Finally, the cervix itself appears at the 
vulva and a complete prolapse of the uterus is present. 

Although perineal lacerations are the most common fore- 
runners of uterine prolapse, there are other factors which assist 
in its causation. Anything which tends to increase the intra- 
abdominal pressure — ascites, chronic constipation, etc. — or 
anything which tends to increase the size of the uterus, will 
help to produce the condition. In rare cases, the cause may 
be congenital laxity of the uterine ligaments and the pelvic 
floor. Such cases are usually accompanied by partial or 
complete enteroptosis. 

On account of these sequefe, every perineal laceration 
should be repaired as soon as possible. 

The Uterus. — The uterus projects upwards and forwards 
into the peritoneal pelvic cavity and separates the utero-rectal 
from the utero-vesical fossa. It measures 3 inches long, 2 
inches wide and 1 inch thick. Under normal conditions, the 
long axis of the uterus meets the long axis of the vagina at an 



59° 



THE GENITO-UR1NARY SYSTEM 



obtuse angle, which is open ventrally, i.e. the uterus is anie- 
verted (Fig. 134). In addition, the body of the uterus is bent 
forwards on the cervix, so that the normal uterus is not only 
anteverted but also anteflexed. 

The uterus consists of a narrow, lower portion, termed the 
cervix, which is continuous above with the body. The free, 
upper extremity of the body of the uterus is known as the 
fundus, and, at the junction of the lateral margin of the body 




Fig. 137. 



-The Uterus and the Broad Ligaments, viewed from in front. 
(Turner's Anatomy.) 



/>. Body of uterus. 
hi. Hroad ligament. 
c. Cervix uteri. 



/. Fundus uteri. 
o. Ovary. 
/. Ep-oophoron. 



r. Round ligament. 

t. Uterine (Fallopian) 
tube. 



with the fundus, the uterus is joined by the uterine (Fallopian) 

tube. 

The Cervix Uteri is about 1 inch long. Its lowest part 
projects into the cavity of the vagina and is consequently 
termed the vaginal portion. The infra-mural portion of the 
cervix receives the attachments of the vaginal walls, while the 
supra-vaginal portion projects upwards above the vagina. It 
should be observed that, whereas the supra-vaginal portion of 
the cervix is covered by peritoneum on its posterior aspect, it 
receives no such covering on its anterior aspect, which is only 
separated from the bladder by some connective tissue. 

The Body of the Uterus is related, anteriorly, to the bladder 



THE UTERUS 391 

and the contents of the utero-vesical peritoneal fossa and, 
posteriorly, to the rectum and coils of small intestine or pelvic 
colon. The lateral border of the body is related to the broad 
ligament and to the uterine artery (p. 392). 

The Ligaments of the Uterus. — In addition to the broad 
ligaments (p. 385), the uterus is more or less fixed in position 
by two round ligaments and two utero-sacral ligaments. The 
round ligament is a fibro- muscular band, which is attached to 
the uterus near the point where it is joined by the uterine 
tube. It passes downwards and laterally between the two 
layers of the broad ligament and reaches the abdominal 
inguinal ring (int. abdom. ring, p. 377), where it enters the 
inguinal canal. Just outside the subcutaneous inguinal ring 
(ext. abdom. ring) the round ligament is attached to the skin 
and fascia in the neighbourhood of the pubic tubercle (spine). 
By exerting a certain slight amount of traction on the upper 
part of the body of the uterus, the round ligament assists in 
maintaining the normal position of the organ. Consequently, 
one of the surgical procedures adopted in the treatment of 
retroversion of the uterus is shortening of the round ligaments. 

The utero-sacral ligaments are attached to the posterior 
aspect of the lower part of the body of the uterus and they 
extend backwards, raising ridges on the peritoneum, on each 
side of the rectum. By exerting slight backward traction, 
these ligaments maintain the normal degree of anteflexion, but, 
if they become contracted and shortened following inflam- 
matory processes, they produce acute anteflexion of the uterus 
by drawing backwards the point of union of the body of the 
uterus with the cervix. In this displacement, the contractions 
of the uterus cannot readily expel the contents during men- 
struation and the contractions become more violent, giving 
rise to referred pains which may be exceedingly severe. 

Displacements of the Uterus. —In addition to acute 
anteflexion, retroversion, with or without some degree of 
retroflexion, may also occur. These conditions are only 
possible when the utero-sacral and round ligaments are 



392 THE GENITO-URINARY SYSTEM 

abnormally lax, and they give rise to the same symptoms of 
referred pain as acute anteflexion. If, however, the retro- 
verted uterus becomes pregnant, as the organ enlarges it is 
caught below the promontory of the sacrum and prevented 
from ascending into the abdomen. Under' these circumstances, 
the enlarging uterus exercises pressure on the other pelvic 
viscera, which cannot get out of the way as they are anchored 
in position by the peritoneum. Constipation is present but 
does not necessarily attract the patient's attention. On the 
other hand, frequency of micturition becomes very oppressive 
and warns the patient that all is not well. If the retroverted 
gravid uterus is replaced in the normal position of anteversion, 



Fig. 138.— Diagram of a Transverse Section through the Uterus 
and the Broad Ligaments, near the lower borders of the latter, 
showing the relation of the uterine artery to the ureter. 

the pregnancy will then in all probability pass to full time, but, 
unless this is effected, abortion at or shortly after the third 
month is inevitable. 

The Blood-supply of the Uterus is derived from the 
uterine and the ovarian arteries (p. 395). The uterine artery 
arises from the hypogastric (internal iliac) and runs forwards 
across the floor of the pelvis till it reaches the base of the 
broad ligament. It then turns and runs medially in the lowest 
part of the broad ligament, and three-quarters of an inch from 
the uterus it crosses above and in front of the ureter, as the 
latter passes forwards to reach the bladder. On reaching the 
lateral aspect of the cervix, the uterine artery gives off a small, 
descending vaginal branch and turns upwards along the lateral 
border of the' uterus to supply the organ. In the operation of 



THE UTERUS 393 

hysterectomy, ligature of the artery is carried out in the interval 
between the point where it crosses the ureter and the point 
where it gives off its vaginal branch. The greatest care must 
be taken to avoid including the ureter in the ligature. The 
pulsations of the uterine artery may be felt when the fingers 
are examining the lateral vaginal fornix. 

The Lymph Vessels from the body and fundus of the 
uterus terminate in the lumbar and the external iliac lymph 
glands for the most part, but a few pass along the round 
ligament and reach the superficial subinguinal group (p. 388). 
The lymph vessels from the cervix pass to the hypogastric and 
the external iliac lymph glands (p. 388) and also to the lymph 
glands which lie on the anterior aspect of the sacrum. 

The Nerves of the Uterus are mainly derived from the 
hypogastric plexus of the sympathetic, and they are ultimately 
derived from the lower three thoracic and the first lumbar 
segments and the second, third and fourth sacral segments. 
The relation of the viscero-sensory reflex of Mackenzie to 
uterine pain has not been at all fully worked out. When the 
uterus gives rise to referred pains, they are usually experienced 
in the regions supplied by the posterior rami of the lower 
thoracic nerves (Fig. 60), but the areas supplied by the anterior 
rami are sometimes affected. As in the case of other viscera 
supplied from the sacral part of the spinal medulla, referred 
pains are usually experienced in the perineum and only very 
rarely in the lower limb. 

The Ovary. — The ovary lies between the two layers of the 
broad ligament and projects backwards from the posterior 
layer (Fig. 135). Some authorities do not regard the ovary as 
lying between the two layers, on the ground that its surface is 
covered not by peritoneal endothelium but by germinal epi- 
thelium. The small fold which connects the ovary to the 
posterior layer of the broad ligament and transmits its vessels 
and nerves is termed the mesovarium. In the nullipara the 
ovary lies with its long axis nearly vertical in a small peritoneal 
depression,Tthe fossa ovarica, on the side of the pelvis. In 



394 



THE GENITO-URINARY SYSTEM 



this situation the lateral surface of the ovary is related to the 
obturator nerve, which runs forwards extra-peritoneally across 
the floor of the fossa ovarica. Pelvic inflammation in this 
region may result in pressure on the obturator nerve and re- 
ferred pain may be experienced along the medial side of the 
thigh (Fig. 7). 

The medial surface of the ovary is related to the uterine 
(Fallopian) tube, which is attached by one of its fimbriae to 
the upper ovarian pole. The lower pole of the ovary is 




Fig. 139. — The Broad Ligaments of the Uterus, viewed from behind. 
The uterus has been cut in a frontal (coronal) plane. (Turner's 
Anatomy.) 



b. Body of uterus. 
bl. Broad ligament. 

c. Cervix uteri. 



f. Fundus uteri. 
p. Ovary. 

pi. Ovarian ligament. 
v. Vagina. 



/. Ep-oophoron. 
r. Round ligament. 
t. Uterine tube. 



attached to the upper lateral angle of the uterus by a fibro- 
muscular band, which is termed the ligamentum ovarii proprium. 
In pregnancy the ovary is carried upwards with the enlarging 
uterus out of the pelvis into the abdominal cavity, but its 
relation to the broad ligament does not undergo any important 
alteration. On the other hand, when cysts develop in the 
ovary, the organ ascends from the pelvis but it remains anchored 
to the broad ligament by the mesovarium (p. 386), which 
becomes somewhat elongated to form the pedicle of the cyst. 
This pedicle contains the nerves, lymph and blood-vessels of 



THE OVARY 395 

the ovary, and the last-named are naturally much increased in 
size. Owing to the constant alteration of the positions of 
many of the abdominal viscera, the ovarian cyst may be twisted 
on its pedicle in such a way as to cut off its blood-supply. 
This condition at once produces symptoms which are similar 
to those arising in cases of strangulated hernia. The simi- 
larity of the symptoms is due to the similarity in nerve-supply, 
for both viscera are supplied by sympathetic fibres which have 
their origin in the lower thoracic segments. In this connexion 
it is interesting to observe that in certain cases the differential 
diagnosis between pain induced by inflammation of the 
vermiform process (appendix) and pain having its origin in the 
right ovary may be extremely difficult. 

The Ovarian Artery arises from the abdominal aorta 
and descends to the pelvis on the surface of the psoas major. 
It enters the broad ligament by passing between the two layers 
of the suspensory ligament of the ovary at a point where they 
separate from one another on the lateral wall of the pelvis 
(Fig. 138). Running medially, it supplies branches to the 
uterine (Fallopian) tube, some of which extend medially to 
anastomose with the uterine artery, but the main part of the 
ovarian artery enters the mesovarium to reach the hilum of 
the ovary. When the ovaries and tubes are removed together 
with the uterus, ligature of the uterine and ovarian vessels is 
one of the first steps of the operation. The latter are secured 
by clamping the suspensory ligament of the ovary. 

The ovarian lymph vessels terminate in the lumbar lymph 
glands. 

The Uterine (Fallopian) Tube. — The uterine tube lies in 
the upper border of the broad ligament, but its lateral 
extremity projects freely into the pelvic cavity. This 
extremity of the tube is more or less funnel-shaped, and the 
walls of the funnel are formed by a number of narrow pro- 
cesses, termed the fimbriae. One of these fimbria? is attached 
to the upper pole of the ovary, so that the two structures are 
never far removed from one another. At the bottom of the 



396 THE GENITO-URINARY SYSTEM 

funnel is a small opening, the ostium abdominale, through 
which the lumen of the tube communicates directly with the 
peritoneal cavity of the pelvis, and at the margin of the orifice 
the endothelium of the peritoneum merges into the columnar 
ciliated epithelium of the tube. 

When ovulation occurs and an ovum is discharged from the 
ovary, it passes at once into the general peritoneal cavity. If it 
does not come into contact with one of the fimbria?, it is 
absorbed, but if it does do so, it may succeed in entering the 
ostium abdominale and it is then carried medially towards 
the uterus by the action of the cilia? lining the uterine tube. 
According to current beliefs, the ovum, if it is destined to 
become fertilised, undergoes that change within the tube and 
is then carried onwards into the uterine cavity, which is ready 
to receive it by the time it leaves the tube. 

Ectopic Gestation. — Under abnormal conditions, the 
impregnated ovum may fail to reach the uterus, and, in that 
event, it goes on developing in the tube, giving rise to the 
tubal type of ectopic gestation. As the ovum enlarges, the 
wall of the tube becomes gradually thinned out, and between 
the sixth and eighth week it ruptures. The seriousness of the 
condition depends on the exact site of the rupture. If the 
rupture involves the upper surface of the tube, the peritoneum 
covering it is also affected, and an intra-peritoneal haemorrhage 
occurs which calls for instant surgical interference. On the 
other hand, the lower surface of the tube may rupture and, in 
this case, the subsequent haemorrhage occurs between the two 
layers of the broad ligament. As a result, it is more restricted 
in amount and the condition, though by no means trivial, is 
not so serious. 

Just as the ostium abdominale allows the passage of the 
ovum from the peritoneal cavity into the uterine tube, so it 
may permit septic infection to spread directly from the tube 
to the peritoneal cavity and, indeed, by way of the vagina, 
uterus and uterine tube, infection may ascend from the 
exterior to the pelvic peritoneal cavity. The presence of 



THE MULLERIAN DUCTS 



397 



pus in the utero-rectal fossa can always be determined by 
palpation of the posterior fornix of the vagina. 

Congenital Anomalies of the Female Pelvic Viscera. 
— Before the various congenital anomalies are described, it is 
necessary to give a brief outline of the normal developmental 
history of the female organs of generation. 

The Miillerian ducts, which leave very few remains in the 
male (p. 381), form practically the whole of the uterine tubes, 
the uterus and the vagina. Their mode of origin is curious, as 
the ostium abdominale is the first part to appear. A surface 
depression occurs in the lining membrane of the body cavity, 

L'terine tube (Miillerian duct) 



L T teru> 
(fused Miillerian ducts)' 



Vagina_ _ 
(fused Miillerian ducts) - " 




,''-'lnnfl7'~ - -Ep-oiiphoron 
// (Wolffian duct) 



if-—-. Duct of Gaertncr 
~ (Wolffian duct) 



Fig. 140. — Diagram of the De%elopment of the Female Generative Organs. 
The dotted lines represent the part of the Wolffian duct which normally disappears. 

lateral to the Wolffian body (p. 380), and it burrows its way 
tailwards, still retaining its connexion with the body cavity — 
a connexion which, as already noticed, exists throughout life. 
After a time, the two Miillerian ducts approach one another 
by passing medially in front of the Wolffian duct and the 
gut, and their caudal portions unite. About this time the 
caudal end of the tube opens into the urogenital sinus, but, 
later, owing to a difference in the relative rates of growth, 
the urethra and the vagina acquire independent orifices on 
the surface of the perineum. 

The proximal unfused ends of the Miillerian ducts form the 
uterine tubes ; the fused portions form the uterus and vagina. 



398 THE GEN1TO-URINARY SYSTEM 

The process of fusion may not be carried out in its entirety, 
and varying degrees of failure are found. In the simplest 
variety, the vagina is subdivided into right and left halves by 
a median partition, and the condition may or may not be 
associated with a bicornuate or bipartite uterus. The pos- 
sibility of the presence of a bicornuate uterus must always be 
borne in mind in obstetrical and gynecological practice, as it 
is by no means a great rarity. 

The ovary is developed from the reproductive gland (p. 380), 
which arises in the lumbar region in close relation to the 
kidney. As a result, it obtains its blood-supply direct from 
the abdominal aorta and its nerves from the lower thoracic 
part of the spinal medulla. It is not till the later stages 
of foetal life that the ovary becomes pelvic in position. 
Although in this way striking similarities exist between the 
testis and the ovary, yet malposition of the ovary is extremely 
rare as compared with malposition of the testis. 

The Ep-oophoron (Parovarium), which lies in the broad 
ligament below the uterine tube, is a vestigial structure. It 
represents a few persisting tubules of the Wolffian body. 
These tubules open into a longitudinal duct, which is usually 
blind at both extremities, but which may descend along the 
lateral margin of the uterus, subsequently opening into the 
vagina. It is termed the duct of Gaertner, and it represents 
the persisting part of the Wolffian duct. The ep-oophoron 
may be the site of cystic enlargement, and such enlargement 
occurs between the two layers of the broad ligament. If the 
tumour is a large one, the uterine tube is found to be 
stretched across its superior aspect and the ovary is attached 
to its posterior aspect by means of the mesovarium, which, 
however, may practically be incorporated with the peritoneal 
covering of the tumour. 

The Female Bladder differs slightly from the corresponding 
organ in the male with regard to its position. Owing to the 
absence of the prostate, the neck of the bladder comes into 
relation with the upper fascia of the urogenital diaphragm 



THE URETHRA 399 

(deep layer of the triangular ligament), and it, therefore, 
occupies a lower position, but in size and shape there is little 
difference. The superior aspect of the bladder is normally in 
relation to the anterior surface of the uterus, but the utero- 
vesical pouch of the peritoneum intervenes. On the other 
hand, the posterior surface of the bladder is in direct contact 
with the anterior aspect of the supra-vaginal part of the cervix 
and the anterior wall of the vagina (Fig. 134). 

The urethra, in the female, is only 1 to i\ inches long, and 
as it passes from the internal to the external orifice it follows 
a slightly curved course, the concavity of the curve being 
directed forwards. The tube is remarkable owing to its 
dilatability. Stones of large size may be passed per urethram, 
and the channel can be dilated so as to render direct ex- 
amination possible both of the vesical mucosa and of the 
ureteral openings. The external orifice of the urethra lies 
about 1 inch posterior to the clitoris and immediately in front 
of the orifice of the vagina. Both lie between the labia 
minora. 

The para-urethral glands lie in the submucous tissue of the 
urethral wall. They are of interest because, though small, 
they are believed to be homologous with the glandular tissue 
of the prostate. They open on the surface by a single duct, 
on each side, just lateral to the external orifice of the urethra. 



VII 
THE DUCTLESS GLANDS 

Under the heading of the ductless glands are included the 
hypophysis (pituitary body), the thyreoid, the parathyreoids, 
the glomus caroticum (carotid body), the thymus, the spleen, 
the supra-renals and the glomus coccygeum (coccygeal body). 
It must be remembered, however, that many of the glands 
which possess ducts do not excrete all their secretion through 
these ducts, and that a part of their secretion is carried away 
by the blood-stream. In this way, the ovary, testes, pancreas, 
etc., all behave after the manner of ductless glands. Further, 
although, like other parts of the body, they are subject to 
numerous pathological changes, the nature of their secretions 
may be so changed as to alter their controlling influence with- 
out producing any recognisable change in the gland itself. On 
the other hand, such grave conditions as exophthalmic goitre 
and splenic anaemia are accompanied by striking alterations 
in the glands concerned. 

The Hypophysis (Pituitary Body). — The hypophysis 
lies in a fossa on the superior aspect of the body of the 
sphenoid. Above, it is attached by a small stalk to the tuber 
cinereum in the interpeduncular fossa (p. 16), and it is 
partially roofed in by a small process of dura mater (Fig. 56). 
This connexion with the brain indicates in part the develop- 
ment of the gland, for its posterior lobe develops as a down- 
growth from the floor of the third ventricle. The anterior 
lobe develops as an up-growth from the roof of the pharynx, 

with which it soon loses all connexion. It was formerly 

400 



THE HYPOPHYSIS 401 

believed that only the anterior lobe of the hypophysis was 
functionally active, but it is now known that the posterior lobe 
also possesses an internal secretion. 

On each side, the hypophysis is related to the cavernous 
sinus and the important structures which are contained in its 
walls (p. 116), namely, the third, fourth, ophthalmic division 
of the fifth, and the sixth cerebral nerves and the internal 
carotid artery. Anteriorly, the hypophysis is related to the 




Fig. 141. — Radiogram of Skull, showing a normal hypophyseal 
(pituitary) fossa. (From Knox's Radiography.) 

optic chiasma (Fig. 8). These relations are of importance, 
as the results of pressure upon them may be of great help in 
the diagnosis of enlargement of the gland. In the majority 
of cases of acromegaly in which the hypophysis has been 
examined, it has been found to have undergone some patho- 
logical change, frequently of the nature of tumour growth. 
The optic chiasma is most commonly affected, and cases of 
bitemporal hemianopia are usually due to this cause ; crossed 
hemianopia or binasal hemianopia may also occur. Affections 
26 



402 



THE DUCTLESS GLANDS 



of the third, fourth and sixth nerves, or of combinations of 
these nerves, especially when the paralysis is bilateral, should, 
in the absence of basal meningitis, suggest the possibility of 
enlargement of the hypophysis. 

Inferiorly, a thin plate of bone separates the hypophysis 
from the sphenoidal air-sinuses (Fig. 114), and, when the gland 




Fig. 142. — A much enlarged Hypophyseal Fossa, caused. by a tumour 
of the Hypophysis (pituitary body). (From a Radiograph taken 
by Dr. S. G. Scott.) 

enlarges, this plate becomes so thin that it can easily be 
removed during the operation of excision of the gland. The 
sphenoidal sinuses act as a convenient landmark in lateral 
radiograms of the skull, and the hypophyseal fossa can 
usually be made out without great difficulty. In those cases 
in which the optic chiasma is affected, an increase in the 
antero-posterior extent of the fossa may be expected, but when 
the tumour grows in a lateral direction, no sign of alteration 
may be found in radiograms of the skull. 



THE SPLEEN 403 

The Spleen. — The spleen lies mainly in the left hypo- 
chondriac region, in contact with the left cupola of the 
diaphragm. Under normal conditions it is exceedingly 
pliable, and its shape is moulded according to the pressure 
exerted by the stomach and the left (splenic) flexure of the 




Fig. 143. — The Spleen and the Left Kidney and Ureter outlined on 
the Dorsal Aspect of the Body. The lower border of the left lung 
and the lower limit of the left pleural sac are also shown. 

colon, which wedge it against the diaphragm and the left 
kidney. With the exception of a small strip at the hilum, it is 
entirely covered by the peritoneum of the greater sac, and it 
is attached to the fundus of the stomach and the anterior 
surface of the left kidney by the gastro-splenic and the lieno- 
renal ligaments, respectively (Fig. 144). 

The diaphragmatic surface of the spleen is gently convex, 



404 THE DUCTLESS GLANDS 

and possesses superior, anterior and posterior angles. The 
superior angle is only i| to 2 inches lateral to the median 
plane and is on a level with the tenth thoracic spine. The 
anterior angle lies in the ninth intercostal space in the posterior 
axillary line, while the posterior angle lies on the eleventh rib. 
This surface, in its whole extent, is separated by the diaphragm 
from the lower part of the left pleural sac, and its upper part is 
also under cover .of the lower border of the left lung. Percus- 
sion of the diaphragmatic surface of the spleen is rendered 
exceedingly difficult on account of the number of structures 
which intervene between it and the surface of the body. They 
include the diaphragm, the pleural sac, the thoracic parietes, 
the latissimus dorsi muscle and, over the superior part, the 
lung and the sacro-spinalis muscle, in addition. It should be 
remembered that, ivhen the spleen is normal in size and position, 
it cannot be palpated, as it lies under cover of the left costal 
margin, and that only its anterior half can be determined by 
means of percussion. 

The anterior border of the spleen extends from the superior 
to the anterior angle and it almost invariably possesses one or 
more notches (Fig. 125). These notches may be of help in 
determining the nature of a tumour on the left side of the 
abdomen {vide infra). 

The gastric surface of the spleen is separated from the 
diaphragmatic surface by the anterior notched border, and 
from the renal surface by the hilum. The inferior surface of 
the spleen is in contact with the left flexure of the colon and 
with a peritoneal fold, termed the phrenico-colic ligament, 
which extends from the flexure to the diaphragm. This fold 
is of great importance to the clinician, for it accounts for the 
direction in which the spleen passes as it enlarges. It prevents 
enlargement in a purely downward direction, and makes the 
organ pass forwards and downwards. 

Splenic Enlargement. — As the spleen enlarges, the diaphrag- 
matic surface increases in extent until it projects beyond the 
costal margin and comes into contact with the muscular anterior 



THE SPLEEN 



405 



abdominal wall. But the anterior angle can be palpated while it 
is still under cover of the ribs by pressing upwards and back- 
wards during expiration. When it leaves the costal margin, 
the spleen passes obliquely across the abdomen in direct con- 
tact with the anterior wall so that it can be both palpated and 
percussed very easily. The obliquity of the anterior border of 
a tumour in the left half of the abdomen and the presence 
upon it of one or more notches is sufficient to justify the 
diagnosis of splenic enlargement. 




Fig. 144. — Transverse Section through the Abdomen at the level of 
the epiploic foramen (of Winslow), to show the disposition of 
the peritoneum and the connexions of the spleen. 

In this section the stomach is cut along the line A (Fig. Sg). 



I. Stomach. 

II. Epiploic foramen. 
IV. Right kidney. 

V. Left kidney. 
VI. Spleen. 



VII. Omental bursa (lesser 
sac). 

2. Lieno-renal ligament. 

3. Gastro- splenic liga- 

ment. 



4. Aorta. 

5. Hepatic artery. 

6. Portal vein. 

7. Inferior vena cava. 

8. Bile duct. 



The dulness produced by an enlarged spleen may merge 
with the liver dulness, but a A-shaped notch can usually be 
demonstrated between the two viscera. 

In rupture of the spleen it is usually the diaphragmatic 
surface which is involved, and the haemorrhage occurs 
directly into the greater peritoneal sac (Fig. 144). 

The spleen obtains its blood-supply from the splenic artery., 
which is one of the branches of the ceeliac artery. The 



4 o6 THE DUCTLESS GLANDS 

splenic vein receives tributaries from the stomach and the pan- 
creas, and, near its termination, it is joined by the inferior 
mesenteric vein. Finally, it unites with the superior mesenteric 
vein to form the vena portse. In portal obstruction, the 
splenic vein shares in the obstruction, and the resulting venous 
congestion of the spleen causes definite enlargement of that 
organ (p. 274). 

In addition to pouring its blood into the portal circulation, 
the spleen undergoes slow, rhythmic contractions, which 
greatly assist the flow of blood through the portal system. 
These contractions occur once per minute and they dis- 
appear altogether when the spleen becomes enlarged. Very 
little is known with regard to the mechanism by which the 
contractions are controlled, but, when the organ becomes in- 
creased in size, the contractions either diminish or disappear 
entirely, so that they are of little help from the point of view 
of diagnosis. 

Movable spleen, though uncommon, is a well-recognised 
condition. It usually occurs in association with complete 
visceroptosis (cf. p. 389), and is due to the increased extent and 
laxity of its peritoneal connexions, namely, the gastro-splenic 
and the lieno-renal ligaments. The condition, per se, is of 
little or no importance, but it may be accompanied by pain 
due to stretching of the peritoneum (cf. movable kidney, p. 360). 
It sometimes happens that the lieno-renal ligament becomes 
twisted and this produces kinking of the contained splenic vein. 
As a result, the organ becomes greatly distended and the con- 
dition is apt to be mistaken for an ovarian cyst with a twisted 
pedicle. The mistake, however, is of little consequence, since 
both conditions call for immediate surgical interference. 

The operation of complete splenectomy has been carried out 
for movable spleen and after rupture of the viscus, and it 
is not followed by any grave disturbance in the general 
state of health. 

Puncture of the Spleen. — When it is desired to obtain a 
specimen of the blood in the interior of the spleen, a hypo- 



THE SUPRA-RENAL GLANDS 



407 



dermic needle may be passed into its substance without any 
bad after-effects. As a general rule, under these circumstances, 
the organ is enlarged and its diaphragmatic surface, being in direct 
contact with the anterior abdominal wall (p. 405), may be reached 
without the risk of injuring any of the neighbouring viscera. 



- — Diaphragm 



.Cardiac end 
of stomach 
Gastric sur- 

' face of spleen 

, Left supra- 
renal gland 

' Left kidney 

' Splenic 
vessels 



— Pancreas 




- "Left kidney 

_Left colic (splenic) 
flexure 



I ___Commencement 

of je uuum 



FlG. 145. — The relations of the Left Kidney and the Viscera, which 
form the " bed " of the Stomach. 



The Supra-renal Glands. — The supra-renal glands lie on 
the upper part of the posterior abdominal wall. They are 
closely related to the upper poles of the kidneys, from which 
they are separated only by a little loose areolar tissue. This 
relationship, however, is purely topographical, for the develop- 



4 o8 THE DUCTLESS GLANDS 

mental histories of the two viscera are very different. As has 
already been pointed out, the kidneys originally develop in 
the pelvic region, and the retention of the pelvic position is a 
well-recognised developmental anomaly. On the other hand, 
the supra-renal glands develop in the abdomen, and they are 
therefore found in their normal position on the posterior 
abdominal wall, even when the kidney lies in the pelvis. 
Histologically, the supra-renal gland consists of two parts, 
which are well differentiated, namely, the cortex and the 
medulla. These two parts differ from one another, not only 
in appearance, but also in their functions and their mode of 
development. Adrenalin is formed in the medulla of the 
gland, while the cortex is functionally passive, and cortical 
extracts have no marked actions, when introduced into the 
body. The medulla of the supra-renal is developed by a 
budding off of some of the cells of the lumbar sympathetic 
system, whereas the cortex is simply a condensation of the 
mesoderm, in which the medullary anlage is situated. This 
connexion of the gland with the sympathetic system is of 
interest in connexion with Addison's disease. 

In the majority of cases, post-mortem examination in 
Addison's disease has revealed some lesion, usually tuber- 
culous in origin, of the supra-renal glands. In a small 
percentage of cases, the supra-renals have been normal in 
appearance and structure, but examination of the cceliac 
ganglia (p. iSS), which lie close to the medial borders of the 
supra-renals, has revealed the fact that they were the site of 
tuberculous disease. In consequence, there are two different 
theories with regard to the cause of Addison's disease. 
The first, and most widely accepted, theory holds that the 
condition is due to some pathological change in the supra- 
renal glands, and that this change leads to alteration in the 
nature of the internal secretion. This theory infers that the 
administration of supra-renal extract is the rational line of 
treatment to adopt. The use of this extract, though some- 
times temporarily beneficial, cannot, however, be regarded as 



THE THYREOID GLAND 409 

curative. The second theory holds that the abdominal 
sympathetic is at fault, and that the occurrence of the disease, 
along with pathological conditions of the gland, is due to the 
formation of adhesions with, and consequent irritation of, the 
cceliac ganglia and their branches. 

The Thyreoid Gland. — The thyreoid gland is, perhaps, 
the most important of all the ductless glands, since it is the 
most frequently affected by pathological conditions. It consists 
of two lateral lobes connected to one another by a narrow 
band of gland substance, termed the isthmus (Fig. 146). The 
isthmus lies in front of the second, third and fourth rings of 
the trachea, and, like the rest of the gland, it is enveloped in 
a fibrous sheath, derived from the pretracheal layer of the deep 
cervical fascia. 

The lateral lobe is pyramidal in shape. The pointed apex 
is superior and lies in contact with the lamina of the thyreoid 
cartilage. The enlarged base is inferior and extends downwards 
to the level of the sixth or seventh tracheal ring. The deep 
surface of the lateral lobe is in contact with the thyreoid and 
cricoid cartilages and the upper six or seven rings of the 
trachea, but it usually extends farther backwards and comes 
into relationship with the inferior constrictor of the pharynx 
and the oesophagus. Its lower part, therefore, is related to 
the recurrent (laryngeal) nerve, which ascends in the groove 
between the trachea and the cesophagus and disappears under 
cover of the inferior constrictor (Fig. 49). 

Tumours of the Thyreoid Gland. — When the thyreoid gland 
becomes enlarged, the effects are mainly produced on the 
deep relations. There may be difficulty in respiration owing 
to pressure on the trachea, but, owing to the strength of the 
tracheal walls, this symptom may be preceded by dysphagia. 
In addition, one or both recurrent nerves may be involved, 
and irritation of them leads to unilateral or bilateral abductor 
paralysis (p. 338). Section of the thyreoid isthmus is sufficient 
to do away with the respiratory embarrassment, since it removes 
the constricting band. 



4io 



THE DUCTLESS GLANDS 



The anterolateral surface of the gland is placed under 
cover of the sterno-thyreoid, sterno-hyoid and omo-hyoid 
muscles. These muscles become stretched out, forming a 
thin sheet over the gland when it is enlarged. On this 




Fig. 146.— Transverse Section through the Neck at the level of the 
First Thoracic Vertebra. 



Isthmus of thyreoid gland. 
Sterno-hyoid and sterno- 
thyreoid muscles. 
Right lobe of thyreoid gland. 
Sterno-mastoid muscle. 



5. Right recurrent nerve. 

6. Internal jugular vein. 

7. Common carotid artery. 

8. (Esophagus. 

9. First thoracic vertebra. 



account, the gland becomes very superficial and can readily 
be palpated. 

The posterior surface of the gland overlaps the antero- 
medial aspect of the carotid sheath, which may be thrust 
deeply under cover of the sterno-mastoid when the gland is 



THE THYREOID GLAND 411 

enlarged. In some cases, tumours of the thyreoid may 
transmit the pulsations of the carotid artery. 

The internal secretions of the thyreoid gland are of the 
greatest importance in controlling and regulating the tissue- 
changes of the body. Congenital absence of the gland causes 
the condition of cretinism, in which the subject is backward in 
growth, both mentally and bodily. Myxcedema arises when 
the secretions of the thyreoid, hitherto normal in character 
and sufficient in amount, undergo alterations, leading to 
changes in both the mental and the physical conditions of 
the patient. These involve a curious overgrowth of the 
superficial fat in certain regions of the body, notably in the 
face and in the lower part of the posterior triangle of the neck. 
The opposite condition, thyreoidism, is most frequently seen 
in exophthalmic goitre. It is also met with after operations 
which have involved incisions into the gland, and it then 
arises from absorption of the secretion which is poured out 
from the cut surface. The condition is characterised by a 
rapid and weak pulse, rapid and shallow respirations, tremor 
and other signs of great nervous excitability. It is said that 
removal of the thyreoid gland alone does not cause myxcedema, 
and it is suggested that the parathyreoids (p. 412), if left 
behind, are able to carry out all the duties of the thyreoid 
gland. 

Development of the Thyreoid Gland. — The thyreoid 
gland arises as a downward-growing hollow bud in the floor 
of the primitive pharynx, and its connexion with the mouth 
remains as the foramen ccecum, a small blind pit situated in the 
middle line on the dorsum of the tongue, at the junction of its 
middle and posterior thirds. The bud grows downwards in 
front of the larynx, loses its lumen and enlarges to form the 
isthmus and the lateral lobes. The connexion between the 
foramen caecum of the tongue and the isthmus of the thyreoid 
is known as the thyreo-glossal duct, and it may persist either 
in a part or in the whole of its extent. When persistent, it 
may give rise to a thyreo-glossal cyst, which may extend 



412 THE DUCTLESS GLANDS 

upwards above the hyoid bone into the substance of the 
tongue. Such cysts lie superficial to the larynx and are easily 
felt in the anterior median line of the neck. They may lie 
superficial to the hyoid bone, but, as the thyreo-glossal duct 
frequently passes through the hyoid bone, they may be con- 
stricted at this point. 

The thyreoid gland receives two arteries on each side. The 
superior thyreoid, which arises from the external carotid, is 
chiefly distributed to the upper pole and the upper border of the 
isthmus, while the inferior thyreoid, which arises from the first 
part of the subclavian artery, supplies the lower two-thirds of 
the lateral lobe and the inferior border of the isthmus. The 
superior and middle thyreoid veins pass laterally to join the 
internal jugular vein, but the inferior group descend in front 
of the trachea to terminate in the left innominate vein. The 
position of the latter group is of great importance in connexion 
with the operation of low tracheotomy, on account of the 
danger of the inspiration of blood into the terminal bronchi. 

The lymph vessels of the thyreoid gland, for the most part, 
terminate in the lower anterior group of the deep cervical 
lymph glands (p. 352), but some of them descend along the 
trachea and join the paratracheal and the mediastinal lymph 
glands. 

The Parathyreoid Glands are four in number. They lie 
within the fascial sheath of the thyreoid gland in close relation 
to the posterior aspects of the lateral lobes, and it is believed 
that they are able to assume and carry on the functions of 
the thyreoid gland after thyreoidectomy. It has also been 
suggested that the parathyreoid glands are at fault in tetany 
and in paralysis agitans. 

The Thymus Gland. — The thymus gland lies in the lower 
part of the neck and in the superior mediastinum. Its history 
is complicated by the numerous variations which may occur 
from what is believed to be the normal standard. At birth 
the gland is relatively large and is responsible for the large 
area of dulness which is found on percussion over the upper 



THE THYMUS 413 

part of the sternum. It enlarges fairly rapidly during the first 
few years of life, but from infancy to the onset of puberty 
its rate of growth is much slower. Thereafter it rapidly 
decreases, and, in adult life, it may be represented merely by 
a few fibrous strands in the superior mediastinum. It must 
be remembered, however, that it is by no means uncommon 
for the thymus gland to retain its original size throughout 
life, and this condition is much commoner in females than 
it is in males. 

Tumours of the Thymus Gland. — Even the fibrous remnants 
of the gland may give rise to a mediastinal tumour, and such 
a condition is frequently found in exophthalmic goitre. The 
symptoms depend on the relations of the gland. Venous 
engorgement is commoner on the left side of the head and 
neck and upper limb, as the gland lies anterior to the left 
innominate vein. Since the gland lies immediately behind the 
manubrium sterni, the area of dulness to which it gives rise is 
quite definite. Further, the gland is closely related to the 
upper border of the aortic arch and to the large branches 
which arise from it. On this account, it may be difficult to 
distinguish the tumour from an aneurism, when it is palpated 
in the jugular (supra-sternal) notch. Owing to the narrowness 
of the area in which the examination is carried out, it may be 
impossible to determine whether the pulsation is expansile or 
whether it is merely transmitted from the vessels. 

Very little is known with regard to the functions of the 
thymus, and its relation to such conditions as myasthenia 
gravis, in which it is very frequently the seat of pathological 
changes, is not as yet properly understood. 

The Glomus Caroticum (Carotid Body) is a small structure 
which is situated on the dorsal aspect of the bifurcation of the 
common carotid artery. It is richly supplied with blood and 
lymph vessels and it receives numerous branches from the 
sympathetic system. It contains numerous chromophil cells, 
but the nature of the internal secretion is still unknown, and 
the relation of the gland to disease has not been fully studied. 



4 i4 THE DUCTLESS GLANDS 

The Glomus Coccygeum (Coccygeal Body) is a small structure 
which lies on the pelvic surface of the coccyx behind the 
rectum. Although it is usually described as one of the duct- 
less glands, it seems very doubtful whether it is not merely an 
adjunct of the circulatory system, with no special internal 
secretion. 



GLOSSARY 



Old Name. 

Annulus ovalis 
Antecubital fossa 
Appendix, vermiform 
Aqueduct of Sylvius 

Arteries — 

Capsular 

Circle of Willis 

Coeliac axis 

Coronary (of stomach) 

Cremasteric 

Deep epigastric 

Facial 

Gluteal 

Inferior coronary 

dental 
Internal iliac 
Meningeal, small 
Pyloric 
Sciatic 
Spermatic 
Superior coronary 

dental 
Thoracic axis 
Thyroid axis 

AryUeno-epiglottidean folds 
Auricle (of heart) 
Auricular appendix 
Auriculo-ventricular bundle 

groove 

orifice 
Bartholin's glands 
Bicipital fascia 
Bulb of penis 
Capsule of tenon 
Cartilages, semilunar 
Circumvallate papilla; 



B.N.A. 
(or English Translation). 

Limbus fossse ovalis 
Cubital fossa 
Vermiform process 
Cerebral aqueduct 

Arteries — 

Supra-renal 
Arterial circle 
Cceliac 
Left gastric 
External spermatic 
Inferior epigastric 
External maxillary 
Superior gluteal 
Inferior labial 

alveolar 
Hypogastric 
Meningeal, accessory 
Right gastric 
Inferior gluteal 
Internal spermatic 
Superior labial 

alveolar 
Thoracoacromial 
Thyreo-cervical trunk 

Ary-epiglottic folds 
Atrium 
Auricle 

Atrio-ventricular bundle 
Coronary sulcus 
Atrio-ventricular orifice 
Vestibular glands 
Lacertus fibrosus 
Urethral bulb 
Fascia bulbi 
Menisci 
Vallate papilla 



415 



416 



GLOSSARY 



Old Name. 

Cornua (of spinal cord) 
Corpus spongiosum penis 
Cowper's glands 

Crico-thyroid membrane (central 
part) 
(lateral part) 
Crural canal 

ring 
Douglas, pouch of 

semilunar fold of 
Ductus venosus, obliterated 
Eminentia teres 
Epicranial aponeurosis 
Epididymis, globus major of 

minor of 
Fascia, infundibuliform 

intercolumnar 
Fenestra, ovalis 

rotunda 
Fissure, calloso-marginal 

dentate 

parallel 

of Rolando 

of Sylvius 
Flexure, hepatic (of colon) 

splenic (of colon) 
Fossa of Rosenmiiller 
Galen, veins of 

great vein of 
Gangliated cord of sympathetic 
Ganglion, Gasserian 

jugular 

lenticular 

of Meckel 

of root 

semilunar 

of trunk 

Wrisberg 
Gyrus, ascending frontal 
parietal 

callosal 
Highmore, antrum of 
Hunter's canal 
Hydatids of Morgagni 
Ilio-tibial band 
Incisura temporalis 
Inferior (in describing relationships 
in limbs) 



n 



B.N.A. 
(or English Translation) 

Columns 

Corpus cavernosum urethrae 
Bulbo-urethral glands 
Crico-thyr'eoid ligament 

Conus elasticus 
Femoral canal 

ring 
Utero-rectal pouch 
Linea semicircularis 
Ligamentum venosum 
Facial colliculus 
Galea aponeurotica 
Head of epididymis 
Tail of epididymis 
Fascia, internal spermatic 

external spermatic 
Fenestra vestibuli 

cochleae 
Sulcus cinguli 
Hippocampal fissure 
Temporal sulci (superior and 

middle) 
Central sulcus 
Lateral fissure 
Right colic flexure 
Left colic flexure 
Pharyngeal recess 
Internal cerebral veins 
Great cerebral vein 
Sympathetic trunk 
Ganglion, semilunar 

superius 

ciliary 

spheno-palatine 

jugular 

cceliac 

nodosum 

cardiac 
Gyrus, anterior central 

posterior central 

cinguli 
Maxillary sinus 
Adductor canal 
Appendices testis 
Ilio-tibial tract 
Rhinal fissure 
Distal 



GLOSSARY 



417 



Old Name. 

Inter-articular fibro- cartilage 

Intervertebral disc 
Island of Reil 
Lamina cinerea 
Larynx, sinus of 

upper aperture of 
Lesser sac 

Ligaments — 

Anterior annular, of ankle 
of wrist 

common 
Cotyloid 
External annular, of ankle 

arcuate 

lateral, of ankle 
of elbow 
of knee 
( 'limbernat's 
Glenoid 
Inferior calcaneo-scaphoid 

thyro-arytamoid 
Internal annular, of ankle 

arcuate 

lateral, of ankle 
of elbow 
of knee 
Mucosum 
Orbicular 
Ovario-pelvic 
Posterior annular, of wrist 

common 
Poupart's 
Rhomboid 
Sacro-sciatic, great 

small 
Subflavum 
Triangular, superficial layer 

deep layer 

Lobe, caudate (of liver) 

Spigelian 
Marshall, vestigial fold of 
Mastoid antrum 
Meatus, external auditory 

urinarius 
Middle ear 
Monro, foramina of 
27 



B.N. A. 

(or English Translation). 

Articular disc 

Intervertebral fibro-cartilage 

Island 

Lamina terminalis 

Ventricular appendix 

Laryngeal aditus 

Omental bursa 

Ligaments — 

Transverse and Cruciate 

Transverse carpal 

Anterior longitudinal 

Labrum glenoidale 

Peroneal retinacula 

Lateral lumbo-costal arch 

Lateral 

Radial collateral 

Fibular collateral 

Lacunar 

Labrum glenoidale 

Plantar calcaneonavicular 

Vocal 

Laciniate 

Medial lumbo-costal arch 

Deltoid 

Ulnar collateral 

Tibial collateral 

Patellar synovial fold 

Annular 

Suspensory, of ovary 

Dorsal carpal 

Posterior longitudinal 

Inguinal 

Costo-clavicular 

Sacro-tuberous 

Sacro-spinous 

Flavum 

Inferior fascia of uro-genital 

diaphragm 
Superior fascia of uro-genital 

diaphragm 

Caudate process 

lobe 
Ligamentum venae cav.e sinistra 
Tympanic antrum 
Meatus, external acoustic 
External orifice of urethra 
Tympanum 
Interventricular foramina 



4i8 



GLOSSARY 



Old Name. 
Morgagni, columns of 

Muscles — 

Abductor minimi digiti 

pollicis 
Accessorius (of foot) 
Adductor obliquus pollicis 

transversus pollicis 
Ary-vocalis 
Brachialis anticus 
Compressor urethra 
Conjoined tendon 
Crureus 

Ejaculator urinie 
Erector clitoridis 
penis 
spinse 
Extensor ossis metacarpi pollicis 
primi internodii pollicis 
secundi internodii pollicis 
Levator anguli scapulae 
Orbicularis palpebrarum 
Palato-glossus 
pharyngeus 
Pronator radii teres 
Psoas magnus 
Scalenus anticus 

posticus 
Serratus magnus 
Supinator brevis 

longus 
Tendo Achillis 
Tensor fasciae femoris 
Tibialis anticus 

posticus 
Transversalis 
Vastus externus 
internus 

Nasal duct 

Nerves — 
Arnold's 
Auditory 
of Bell 
Circumflex 
Communicans fibularis 

tibialis 
Cranial 
Crural, anterior 



B.N. A. 

(or English Translation). 
Rectal columns 

Muscles — 

Abductor digiti quinti 

pollicis brevis 
Quadratus plantK 
Adductor pollicis, pars obliqua 

pars transversa 
Vocalis 
Brachialis 

Deep transverse perineal 
Falx inguinalis 
Vastus intermedius 
Bulbo-cavernosus 
Ischio-cavernosus 

Ischio-cavernosus 

Sacro-spinalis 

Abductor pollicis longus 

Extensor pollicis brevis 
longus 

Levator scapula.- 

Orbicularis oculi 

Glosso-palatinus 

Pharyngo-palatinus 

Pronator teres 

Psoas major 

Scalenus anterior 
posterior 

Serratus anterior 

Supinator 

Brachio-radialis 

Tendo calcaneus 

Tensor fasciae lata- 

Tibialis anterior 
posterior 

Transversus 

Vastus lateralis 
medialis 

Naso-lacrimal duct 

Nerves — 

Auricular branch of vagus 

Acoustic 

Long thoracic 

Axillary 

Anastomotic peroneal 

Medial sural 

Cerebral 

Femoral 



GLOSSARY 



4*9 



Old Name. 

Nerves, continued— 
Dental 
Dorsal 

External cutaneous, of musculo- 
spiral 
of thigh 
respiratory 
saphenous 
Genito-crural 
crural branch of 
genital branch of 
Intercosto-humeral 
Internal cutaneous, of musculo- 
spiral 
of thigh 
of upper limb 
lesser 
Interosseous, anterior 

posterior 
of Jacobson 
Long buccal 
pudendal 

saphenous 
Malar 
Maxillary, inferior 

superior 
Middle cutaneous, of thigh 
Musculocutaneous, of leg 
Musculo-spiral 
Orbital 

Palmar cutaneous 
Pneumogastric 
Popliteal, external 

internal 
Primary divisions 
Pudic, internal 
Radial 

Recurrent laryngeal 
to Rhomboids 
Sciatic, great 

small 
Small occipital 
Spinal accessory 
Subscapular, long 
Supra-acromial 

clavicular 

sternal 
Tibial, anterior 



B.N. A. 

(or English Translation). 

Nerves, continued — 
Alveolar 
Thoracic 
Dorsal antibrachial cutaneous 

Lateral cutaneous 
Long thoracic 
Suralis 

Genito-femoral 
Lumbo-inguinal 
External spermatic 
Intercosto-brachial 
Dorsal brachial cutaneous 

Medial cutaneous 

Medial antibrachial cutaneous 

brachial cutaneous 
Interosseous, volar 

dorsal 
Tympanic 
Buccinator 
Perineal branch of posterior 

cutaneous of thigh 
Saphenous 
Zygomaticofacial 
Mandibular 
Maxillary 

Intermediate cutaneous 
Superficial peroneal 
Radial 
Zygomatic 
Volar cutaneous 
Vagus 

Common peroneal 
Tibial 
Rami 
Pudendal 

Superficial division of radial 
Recurrent 
Dorsalis scapula; 
Sciatic 

Posterior cutaneous, of thigh 
Lesser occipital 
Accessory 
Thoraco-dorsal 
Supra-clavicular, posterior 

intermediate 

anterior 
Deep peroneal 



420 



GLOSSARY 



Old Name. 

Nerves, continued— 
Tibial, posterior 
Vidian 

Nucleus, lenticular 
Omentum, gastro-hepatic 

gastro-splenic 
Opening in adductor magnus 
Optic disc 
Pacchionian bodies 
Parovarium 
Perforated spot, anterior 

posterior 
Petit, canal of 
Peyer's patches 
Pituitary body 
Pleura, cervical 
Poinum Adami 
Pons Varolii 
Popliteal space 
Receptaculum chyli 
Retinacula of ileo-ca:cal valve 
Ring, external abdominal 

internal abdominal 
Sacro-sciatic foramina 
Santorini, cartilages of 

duct of 
Saphenous opening 
Scarpa's triangle 
Schlemm, canal of 
Semicircular canals, membranous 
Septum, crurale 

lucidum 
Sinus, lateral 

longitudinal, inferior 
superior 

piriformis 

pocularis 

of Valsalva 
Sphenoidal fissure 
Spheno-maxillary fissure 
Spinal cord 
Socia parotidis 
Stenson's duct 
Superior {in describing relationships 

in limbs) 
Taenia semicircularis 
Temporo-maxillary joint 
Tonsil, faucial 
Tube, Eustachian 



B.N. A. 

(or English Translation) 
Nerves, continued — 

Tibial 

of pterygoid canal 

Nucleus, lentiform 
Omentum, lesser 
Gastro-splenic ligament 
Hiatus tendineus 
Porus opticus 
Arachnoideal granulations 
Ep-oophoron 
Perforated substance, anterior 

posterior 
Spatia zonularia 
Intestinal tonsils 
Hypophysis 
Cupula pleurae 
Laryngeal prominence 
Pons 

Popliteal fossa 
Cisterna chyli 
Frenula valvulae coli 
Ring, subcutaneous inguinal 

abdominal inguinal 
Sciatic foramina 
Corniculate cartilages 
Accessor)' pancreatic duct 
Fossa ovalis 
Femoral triangle 
Sinus venosus sclera? 
Semicircular ducts 
Septum femorale 

pellucidum 
Sinus, transverse 

sagittal, inferior 
superior 
Recessus piriformis 
Prostatic utricle 
Aortic sinus 
Superior orbital fissure 
Inferior orbital fissure 
Spinal medulla 
Accessory parotid 
Parotid duct 
Proximal 

Stria terminalis 
Temporo-mandibular joint 
Tonsil, palatine 
Tube, auditory 



GLOSSARY 



421 



Old Name. 

Tube, Fallopian 
Turbinated bones 
Urethra, spongy 
Valve, ileo-ca-cal 
Vas deferens 
Veins of Marshall 

saphenous, internal 
Veins, prostatic plexus of 
Velum interposition 
Vena azygos major 

minor inferior 
superior 
Ventricle, fifth 

lateral, descending horn of 
Verumontanum 
Vieussens, valve of 
Vocal coids, false 

true 
Wharton's duct 
Winslow, foramen of 
Wirsung, duct of 
Wrisberg, cartilages of 



B.N. A. 
(or English Translation). 

Tube, uterine 
Conchffi 

Urethra, cavernous part of 
Valve, colic 
Ductus deferens 
Oblique vein of left atrium 
Great saphenous vein 
Pudendal plexus 
Tela chorioidea 
Vena azygos 
hemiazygos 
accessoria 
Cavum septi pellucidi 
Ventricle, lateral, inferior horn of 
Urethral crest 
Superior medullary velum 
Ventricular folds 
Vocal folds 
Submaxillary duct 
Epiploic foramen 
Pancreatic duct 
Cuneiform cartilages 



I NDEX 



Abdominal tumours, 241, 260, 323. 
Acoustic centres, higher, 0. 
lower, 89. 
meatus, external, 198. 
foreign bodies in, 199. 
referred pain in, 199. 
syringing of, 200. 
nerve, 87. 
radiation. 35. 
Acromegaly, 54, 401. 
Acute anterior poliomyelitis, 46. 
Addison's disease, 408. 
Adenoids, 201, 330. 
Allantois, 286, 369. 
Alternate hemi-an?esthesia, 45. 87. 
Ampulla of Vater, 263, 269. 
Anal canal, 283. 

fissure, 183, 283, 285. 
valves, 283. 
Angina pectoris, 308. 

referred pain of, 192, 309. 
Angio-neurotic redema, 228. 
Anosmia, 16, 50. 
Anterior fontanelle, 42. 
closure of, 43. 
perforated substance. 16. 
Aorta, abdominal, 322. 

aneurism of, 322, 323. 
arch of, 318. 

aneurism of, 319. 
ascending, 318. 

aneurism of, 318. 
sinuses of, 31S. 
thoracic, descending, 322. 
Apical phthisis, 351, 352. 
Appendicitis, pain in, 278, 279. 

viscero-motor reflex in, 279. 
Appendix. See Vermiform process. 
Aqueous humor, 216. 
Arachnoid, 1 10. 



Arch, glosso-palatine. 226. 

pharyngo-palatine. 226. 
Arches of foot, 176. 
Area, aortic, 299. 

bicuspid (mitral), 300. 

pulmonary, 299. 

tricuspid, 300. 
Argyll-Robertson pupil, 54, 67. 
Arterial circle (of Willis), 121. 
Arterio-sclerosis, 218. 
Artery or Arteries — 

anterior ciliary, 21 1. 
spinal, 46. 

basilar, 120. 

carotid, internal, 118, 203. 

centralis retinas, 217. 

cerebral, anterior, 120. 
middle, 119. 

embolus in, 121. 
posterior, 120. 

of cerebral haemorrhage, 33, 119. 

hepatic, 261. 

hypogastric, 305. 

iliac, common, 322. 

innominate, 321. 
aneurism of, 322. 

lenticulo-optic, 119. 

lenticulo-striate, 119. 

middle meningeal, 116. 

ovarian, 395. 

pulmonary, 323. 

splenic, 246. 

uterine, 392. 

vertebral, 120. 
Ary-epiglottic fold, 332. 
Arytenoid cartilage, 330. 
Ascites, 241, 274. 
Astereognosis, 10, 30. 
Asthma, spasmodic, 356. 
Atresia ani, 285, 287. 



423 



426 



INDEX 



Foramen ovale, 293, 303. 
persistent, 306. 
of Winslow. See Epiploic fora- 
men. 
Fornix, 14, 24. 
Fossa, ischio-rectal, 283. 
ovalis, 293. 
ovarica, 393. 
Frontal sinus, 327. 



Gall-bladder, 261. 
development of, 264. 
fundus of, 261. 
nerve-supply of, 264. 
referred pain of, 265. 
Gall-stones, impaction of, 263. 
Ganglion impar, 188. 
Garland's curve, 346. 
Gastric referred pain, 250. 
secretion, 248. 
ulcer, 250. 

perforation of, 242. 
Gastro-colic ligament, 237. 
Gastro-splenic ligament, 238. 
Geniculate body, lateral, 30, 51. 
medial, 19, 89. 
ganglion, 80. 
Genital tubercle, 370. 
Gerota's space, 360. 
Glabella, 7. 
Glaucoma, 214, 216. 
Gleet, 379. 
Glomus caroticum, 413. 

coccygeum, 414. 
Grey rami communicantes, 185. 
Gums, lymph vessels of, 225. 
mucous membrane of. 225. 
Gyrus, angular, 9. 
anterior central, 5. 
blood-supply of, 119. 
lesions of, 6. 
surface marking of, 8. 
cinguli (callosal gyrus), 12. 
fornicatus (limbic lobe), 12. 
hippocampal, 12. 
lingual, 18. 
middle frontal, 8. 
posterior central, 5. 
superior parietal, 9. 

temporal, 9. 
supramarginal, 9. 



Haemalemesis, 274, 275. 
Hemorrhoids, internal, 274, 275, 

284. 
Heart, 292. 

accelerator nerves of, 187. 

action of, 300. 

apex-beat of, 294, 297, 298. 

atria (auricles) of, 292, 293. 

atrio-ventricular orifices of, 293. 

block, 313. 

blood-supply of, 310. 

congenital anomalies of, 306. 

development of, 302. 

dilatation and hypertrophy of, 
297, 298. 

displacement of, 297, 298. 

inhibitory nerves of, 98, 308. 

musculature of, 310. 

nerve-supply of, 307. 

percussion of, 296. 

rhythm, 312. 

sounds, 300. 

surface marking of, 294. 
in child, 298. 

valves of, 293, 294. 

surface marking of, 299. 

ventricles of, 293, 294. 
Hemi-anfesthesia, 35. 
Hemianopia, heteronymous, 54. 

homonymous, 13, 35, 54. 

quadrantic, 13. 
Hemiplegia, 35. 
Herpes zoster, 162. 
Hyaloid membrane, 216. 
Hydrocephalus, 24, 27, ill. 
Hydrothorax, 317. 
Hyperaceusis, 80, 205. 
Hypogastric plexus, 188. 
Hypoglossal nerve, 104. 
Hypophysis, 400. 

relations of, 401. 

stalk of, 16. 

tumours of, 54, 401. 
Hypospadias, 371. 
Hysterectomy, 393. 

Icterus neonatorum, 306. 
Ileo-CKcal valve. See Colic valve. 
Ileum, 255. 
Ilio-tibial tract, 172. 
Insula (of Reil), 10, 30. 
Intentional tremor, 22. 



INDEX 



427 



Internal capsule, 32, 33, 35. 

acoustic fibres of, 89. 

lesions of, 35. 

motor fibres of, 33. 

sensory fibres of, 35. 
Interpeduncular fossa, 16. 
Interventricular foramen, 2, 15, 26. 
Intestine, development of, 27S. 
developmental anomalies of, 285. 
large, 276. 

irrigation of, 284. 

nerve-supply of, 284. 

referred pain of, 285. 
small, 253. 

nerve-supply of, 257. 

referred pain of, 257. 

secretion of, 257. 
Intracranial tension, 42, 113. 
Intraocular tension, 214. 
Intraorbital haemorrhage, 210. 
Intrapontine haemorrhage, 86. 
Iridectomy, 216. 
Iridodonesis, 216. 
Iris, 214. 

nucleus, 52. 
Iritis, 214. 
Isthmus faucium, 226. 

Jaundice, 264. 
Jejunum, 253. 
Joint sense, 43, 45. 
Jugular bulb, 301. 

Kidney, 357. 
capsule of, 360. 
floating, 360. 
movable, 360. 
nerve-supply of, 361. 
palpation of, 360. 
relations of, 357. 
surface marking of, 357. 
tumours of, 361. 

Labia majora, 387. 

minora, 387. 
Labyrinth, membranous, 206. 

osseous, 206. 
Lacrimal apparatus, 208. 

ducts, 208. 

gland, 65, 208. 

nerve-supply of, 209. 

sac, 208. 

secretion, 209. 



Lamina rostralis, 2S. 
Laryngeal intubation, 332. 

paralysis, 338. 

prominence, 330. 
Larvngoscopic examination, 332. 
Larynx, 330. 

aditus of, 331. 

muscles of, 335. 

ventricle of, 334. 

vestibule of, 332. 
Lateral fillet, 89. 

fissure (of Sylvius), 8. 
rami of, 9. 

pyramidal tract, 37. 

ventricle of brain, 2, 23. 
Lead poisoning, 140. 
Lens, crystalline, 215. 
Lentiform nucleus, 32. 
Lesser sac. See Omental bursa. 
Lieno-renal ligament, 239. 
Ligamentum arteriosum, 306. 
Light reflex, 52. 
Limbs, development of, 157. 
Linea semilunaris, 262. 
Liver, 257. 

cirrhosis of, 274. 

development of, 264. 

downward displacement of, 25S. 

in infants, 259. 

inferior border of, 259. 

lobes of, 260. 

nerves of, 264. 

new growth in, 260. 

percussion of, 259. 

referred pain of, 265. 

Reidel's lobe of, 259. 

surface marking of, 259. 

surfaces of, 258, 260. 

transverse fissure of. See Porta 
hepatis. 

tropical abscess of, 258, 265. 
rupture of, 258, 261, 353. 

venous congestion of, 261. 

venous pulsation in, 261. 
Lombardi's "varicose zone of 

alarm," 351. 
Lumbar plexus, 163. 

puncture, 41. 
Lumbo-sacral cord, 170. 
Lung, 34S. 

apex of, 349, 350, 351. 

base of, 352. 



428 



INDEX 



Lung, continued — 

fissures of, 348, 349, 350. 
lobes of, 348, 349. 
lymph vessels of, 353. 
nerve-supply of, 356. 
surface marking of, 349. 
Lymph glands, anterior auricular, 
222. 
deep cervical, 222, 249. 
external iliac, 388. 
hypogastric, 388. 
mesenteric, 240, 256. 
subinguinal, 3S8. 
submaxillary, 221. 
submental, 225. 
Lymphatic duct, right, 324. 

Macula lutea, 218. 

Main en griffe, 149. 

Mandibular nerve, 69. 

Mastoid antrum. See Tympanic 

antrum. 
Maxillary nerve, 67. 

sinus, 327. 
M 'Barney's point, 279. 
Meckel's diverticulum, 285, 286. 
Mediastinal tumours, 315, 413. 
Mediastinitis, 291. 
Medulla oblongata, 21. 
Meibomian glands. See Tarsal 

glands. 
Meniere's disease, 90, 208. 
Meningitis, basal, 54, in. 

cerebro-spinal, 1 1 1 . 
Mesencephalon, iS. 
Mesentery. 240. 
Mesocolon, transverse, 237. 
Mesosalpinx, 386. 
Mesovarium, 386, 394. 
Microcephalus, 43. 
Micturition, act of, 373. 

frequency of, 277, 279, 373- 

reflex, 373. 
Mid-brain, 18. 

haemorrhage in, 39. 
Middle ear, 200. 

inflation of, 202, 329. 
Millard-Gubler syndrome, 86. 
Monoplegia, cortical, 7. 
Motor centres, higher, 5. 

fibres, path of, 37. 
Mouth, 225. 



Mullerian duct, 381, 397. 
Muscle or Muscles — 
of abdominal wall, 161. 
adductor pollicis, 147. 
adductor, of thigh, 169. 
biceps brachii, 134. 

femoris, 174. 
brachialis (anticus), 134. 
brachio-radialis, 140. 
buccinator, 82. 
ciliary bundle, 210. 
coraco-brachialis, 134. 
cremaster, 165, 364. 
crico-arytaenoideus lateralis, 337. 

posterior, 336. 
crico-thyreoid, 97, 335. 

paralysis of, 339. 
crureus. See Vastus intermedins, 
deltoid, 137. 
diaphragm, 354. 

paralysis of, 355. 
digastric, 72, 81. 
dilatator pupilla-, 214. 
dorsal, of forearm, 141. 
extensor carpi radialislongus, 140. 

digitorum brevis, 180. 
longus, 180. 

hallucis longus, 180. 
external oblique, 162. 
flexor carpi radialis, 150. 
ulnaris, 144. 

digitorum longus, 176. 
profundus, 151. 
sublimis, 150. 

hallucis longus, 176. 

pollicis longus, 150. 
gastrocnemius, 175. 
genio-glossus, 107. 
genio-hyoid, 106. 
gluteus maximus, 172. 

medius, 172. 

minimus, 172. 
gracilis, 169. 

of hypothenar eminence, 145. 
inferior oblique (of orbit), 57. 

rectus, 57- 
infraspinatus, 131. 
internal oblique, 162. 
interossei, dorsal, of hand, 147. 

volar (palmar), 146. 
intrinsic, of eye, 58. 
of larynx, 335. 



INDEX 



429 



Muscle or Muscles, continued— 
lateral rectus, 58. 

paralysis of, 60. 
latissimus dorsi, 136. 
levator ani, 184. 

palpebme superioris, 57. 
lumbricals, of hand, 145. 
masseter, 70. 
of mastication, 70. 
medial rectus, 58. 
mylohyoid, 7 2 - 
obturator externus, 169. 

interims, 173. 
occipitalis, 81. 
omohyoid, 106. 

orbicularis oculi (palpebrarum), 
57, 82. 
paralysis of, 57, 82. 

oris, 84. 
of the orbit, 57. 

motor centre for, 8. 

paralysis of, 58- 
palmaris longus, 150. 
papillary, of heart, 293. 
pectineus, 166. 
pectoralis major, 133. 

congenital deficiency of, 134. 

minor, 142. 
of perineum, 184. 
peronseus brevis, 180. 

longus, 179. 

tertius, 1S0. 
plantaris, 175. 
popliteus, 176. 
pronator quadratus, 150. 

teres, 150. 
psoas major, 163. 

reflex contraction of, 279. 
pterygoid, 72. 
quadratus femoris, 173. 
quadriceps femoris, 166. 
rectus abdominis, 161. 

femoris, 166. 
rhomboid, 132. 
sartorius, 166. 
semimembranosus, 174. 
semitendinosus, 174. 
serratus anterior, 132. 
soleus, 175. 
sphincter pupilla?, 214. 

paralysis of, 61. 
stapedius, 205. 



Muscle or Muscles, continued— 
sterno-hyoid, 106. 
stemo-mastoid, 103. 
sterno-thyreoid, 106. 
stylo-hyoid, 82. 
stylo-pharyngeus, 94. 
subclavius, 131. 
subscapulars, 136. 
superior oblique (of orbit), 58. 

paralysis of, 60. 
superior rectus, 57- 
supraspinatus, 131. 
temporal, jo. 
tensor fasciae lata?, 172. 

tympani, 205. 
teres major, 136. 

minor, 137. 
of thenar eminence, 151. 

atrophy of, 47. 
thyreo-hyoid, 106. 
tibialis anterior, I So. 

posterior, 176. 
of tongue, 107. 
transversus, 162. 
trapezius, 103. 
triceps, 140. 
vastus intermedins, 166. 

lateralis, 166. 

medialis, 166. 
vocalis, 336. 
Muscle sense, 43. 
Musculo-spiral paralysis. See 

Radial paralysis. 
Myasthenia gravis, 413. 
Myelitis, transverse, 48. 
Mvxcedema, 411. 

Nasal cavity, 325. 

lateral wall of, 325. 

openings into, 325, 327. 
Nasal duct. See Naso-lacrimal 

duct. 
Nasal septum, 325. 
deviation of, 325. 
Xaso-lacrimal duct, 208, 324. 
Naso-pharynx, 329. 
Nerve or Nerves — 
abducent, 56. 

lesions of, 58, 60. 
accessory, 10 1. 
lesions of, 103. 
neuritis of, 104. 



43o 



INDEX 



Nerve or Nerves, continued — 
acoustic, 87. 

lesions of, 89. 
alveolar (dental) inferior, 75. 

superior, 69. 
ansa hypoglossi, 106. 
anterior crural. See Nerve — ■ 

femoral, 
auriculotemporal, 74. 
axillary (circumflex), 137. 
buccinator (long buccal), 75. 
cerebral, 48. 
chorda tympani, 84. 
cochlear, 87. 

lesions of, 89. 
common peroneal (external 

popliteal), 178. 
of deep sensibility, 122. 
dorsal cutaneous, of forearm, 138. 

of penis, 184. 
dorsalis scapulas, 131. 
of epicritic sensibility, 122. 
external spermatic, 165. 
facial, 79. 

intracranial lesions of, 86. 

nucleus of, 79. 
lesions of, 86. 

peripheral lesions of, 82. 
femoral, 166. 

articular branches of, 166. 

cutaneous branches of, 167. 

motor branches of, 166. 

paralysis of, 167. 
fifth cerebral, 61. 
frontal, 65. 
genito-femoral, 165. 
glosso-pharyngeal, 91. 

lesions of, 92. 

lingual branches of, 92. 

tympanic branch of, 92. 
gluteal, inferior, 172. 

superior, 172. 
hemorrhoidal, inferior, 183. 
hypoglossal, 104. 

lesions of, 107. 

ramus descendens of, 106. 
ilio-hypogastric, 163. 
ilio-inguinal, 163. 
infra-orbital, 69. 
infra-trochlear, 65. 
intercostal, 1 60. 
intercosto-brachial, 160. 



Nerve or Nerves, continued — 
intermediate cutaneous (of thigh), 

167. 
intermedins (of Wrisberg), 80. 
lacrimal, 65. 
laryngeal, external, 97. 

internal, 97. 

superior, 97. 
lateral cutaneous, of forearm, 134. 

of thigh, 165. 
lingual, 75. 
long ciliary, 65. 

thoracic (of Bell), 132. 
lumbo-sacral cord, 170. 
mandibular (inferior maxillary), 

6 .9- 

injection of alcohol into, 69. 

maxillary (superior), 67. 

injection of alcohol into, 68. 
medial cutaneous, of arm, 143. 
of forearm, 144. 
of thigh, 167. 

sural, 176. 
median, 149. 

digital branches of, 151. 

lesions of, 152. 
mental, 75. 

musculo-cutaneous, 134. 
musculo-spiral. See Nerve — 

radial, 
naso-ciliary (nasal), 65. 
obturator, 168. 

lesions of, 170. 
occipital, greater, 124. 

third, 124. 
oculo-motor, 20, 54. 

lesions of, 58, 60. 
olfactory, 48. 
ophthalmic, 64. 
optic, 50. 

course of fibres of, 50. 

lesions of, 52. 
perineal, 1S4. 

peroneal, common (external pop- 
liteal), 178. 

deep (anterior tibial), 1S0. 

superficial (musculo-cutaneous), 
17S. 
petrosal, lesser superficial, 92. 
phrenic, 4, 126, 264. 
plantar, lateral, 178. 

medial, 177. 



INDEX 



431 



Nerve or Nerves, continued — 

popliteal, external. See Nerve — 
common peroneal. 

internal. See Nerve — tibial, 
posterior cutaneous, of thigh, 182. 
of protopathic sensibility, 122. 
of the ptervgoid canal (Vidian), 

68. ' 
pudendal, 1S3. 
radial (musculo-spiral), 138. 

deep branch of, 140. 

paralysis of, 141. 

superficial branch of, 14 1. 
ramus descendens cervicalis, 106. 
recurrent (laryngeal), 99, 338. 

compression of, 99, 338. 
roots, 123. 
saphenous, 167. 
sciatic, 173. 

neuritis of, 181. 

paralysis of, 182. 
sensory, classification of, 121. 
spinal, rami of, 123. 
splanchnic, 187. 
subscapular, upper, 136. 

lower, 136. 
supraorbital, 65. 
suprascapular, 131. 
supratrochlear, 65. 
sural, 176. 
sympathetic, 185. 
thoraco-dorsal, 136. 
tibial, 175. 
trigeminal, 61. 

motor paralysis of, 73. 

sensory root of, 62. 
lesions of, 77. 
trochlear, 20, 55. 

lesions of, 58, 60. 
ulnar, 144. 

deep branch of, 145. 
vagus, 94. 

auricular branch of, 96. 

cardiac branches of, 98. 
lesions of, 98. 

distribution of, 100. 

lesions of, 100. 

neuritis of, 101. 

pharyngeal branch of, 96. 
vestibular, 90. 
volar interosseous, 150. 
zygomatic, 68. 



Nervous system, 1. 

development of, I. 

parts of, 5. 
Neurone, 3. 
Nose, 325. 

meatuses of, 325. 
Nucleus of abducent nerve, 56. 

ambiguus, 91, 94, 101. 

dorsalis, 94. 

of oculo-motor nerve, 39, 54. 
lesions of, 60. 

of trochlear nerve, 55. 

(Edema glottidis, 335. 
(Esophageal bougie, 231. 

plexus, 100. 
(Esophagus, 230. 

blood-supply of, 232. 

nerves of, 232. 

obstruction of, 231. 

radiographic examination of, 232. 
Olfactory bulb, 15. 

centres, higher, 16. 

nerves, 48. 

congenital absence of, 15. 

tract, 15. . 
Olivary nucleus, 21. 
Olive, 21. 
Omental bursa (lesser sac), 237. 

boundaries of, 237. 
Omentum, greater, 236. 

lesser, 236. 
Ophthalmic nerve, 64. 
Ophthalmoscopic examination, 216. 
Optic chiasma, 16, 50. 
lesions of, 54. 
pressure on, 401. 

disc. See Poms opticus. 

nerve, 16, 50. 

radiation, 35. 

tract, 16. 

lesions of, 52. 
Otic ganglion, 70. 
Otitis media, 200, 202. 
Otoscopic examination, 202. 
Ovarian cyst, 394, 406. 

pain, 395- 
Ovary, 393. 

development of, 398. 

ligaments of, 387, 394. 

lymph vessels of, 395. 
Ovulation, 396. 



432 



INDEX 



Palatal paralysis, 96. 
Pancreas, 266. 

accessory duct of, 269. 

annular, 270. 

cysts of, 268. 

development of, 269. 

duct of, 269. 

obstruction of, 269. 

malignant disease of, 268. 

tumours of, 268. 
Pancreatic infantilism, 271. 

secretion, 270. 
Paracentesis abdominis, 241. 

pericardii, 291. 

thoracis, 347. 

of tympanic membrane, 203. 
Paracentral lobule, 12. 
Paralysis, lower neurone, 3. 

upper neurone, 3. 
Paraplegia, 323. 
Parathyreoid gland, 412. 
Parietal tuber (eminence), 9. 
Parieto-occipital fissure, 12. 
Parotid duct, 222. 

gland, 222. 
accessory, 224. 
lymph vessels of, 224. 
Parotitis, 223. 

Parovarium. See Ep-oophoron. 
Pelvis, 381. 

bony, 381. 

conjugates of, 383. 

floor of, 3S4. 

Xcegele, 3S2. 

Roberts, 382. 

spondylolisthetic, 382. 
Penis, development of, 371. 
Pepsin, 248. 
Perforated substance, anterior, 16, 

32- 
posterior, 16. 
Pericardial effusion, 288, 289, 291. 
Pericarditis, 230, 289. 
Pericardium, 288. 

adherent, 291. 
Perilymph, 207. 
Perineum, muscles of, 184. 

rupture of, 388. 
Peritoneum, 234. 

compartments of, 240. 

functions of, 240 

nerve-supply of, 241. 



Peyer's patches. See Tonsil, in- 
testinal. 
Pharyngeal plexus, 96. 

recess, 329. 
Pharynx, nasal part of, 329. 

oral part of, 226. 
Phrenic nerve, 126. 
Phrenico-colic ligament, 404. 
Pia mater, 1 10. 

Pillars of fauces. See Arches, 
glosso palatine and phar- 
yngo-palatine. 
Pituitary body. See Hypophysis. 
Planes of abdomen, 233. 
Pleura, 341. 

nerve-supply of, 347. 
Pleural reflection, lines of, 344. 

sac, lower limit of, 345. 
surface marking of, 343. 
exploration of, 346. 
Pleurisy, diaphragmatic, 348. 
Pleuritic effusion, 345. 
Piica sublingualis, 224. 
Plicae circulares, 256. 
Pomum Adami. See Laryngeal 

prominence. 
Pons (Varolii), 20. 
Porta hepatis, 261. 
Portal circulation, 271. 

obstruction, 274. 

caput Medusae of, 276. 
Porus opticus, 216. 
Pre-auricular point, 8. 
Prepuce, 379. 

adherent, 380. 
Presbyopia, 215. 
Proctodseum, 287. 
Progressive muscular atrophy, 46, 

108, 152. 
Promontory, sacral, 382. 
Prostate, 374. 

hypertrophy of, 374. 
Prostatic utricle, 379. 
Protopathic sensibility, 122. 
Pseudo-bulbar paralysis, 36. 
Pseudo-ptosis, 1S9, 210. 
Ptosis, 57, 60. 
Ptyalin, 225. 
Pudendal plexus, 1S3. 
Pulmonary plexus, 100. 
Pulsation, epigastric, 297. 
Pulse tracing, 301. 



INDEX 



43; 



Pulse tracing, venous, 311. 
Pulvinar, 29, 51. 
Pupillary fibres, 52. 
Pylorus, 242. 

adhesions at, 248. 
Pyramidal tract, 37. 

mode of termination of, 37. 
Pyramids, 21, 37. 

decussation of, 21, 37. 

Radial paralysis, 141. 
Recessus piriformis, 332. 
Rectocele, 389. 
Rectum, 281. 

digital examination of, 283. 

flexures of, 282. 

prolapse of, 283. 

valves of, 282. 
Referred pain, 190. 
Regions of abdomen, 233. 
Reidel's lobe, 259. 
Rennin, 248. 
Residual urine, 374. 
Respiration, movements of, 354. 

types of, 354. 
Restiform body, 21, 22. 
Retention of urine, 48. 
Retina, 214. 
Rima glottidis, 335. 

vestibuli, 333. 
Round ligament of uterus, 391. 

Saccule, 206. 

Sacral plexus, 170, 283. 

pressure on, 171. 
Sacral promontory, 382. 
Salivary glands, 222. 

secretion, 225. 
"Saturday night" paralysis, 138. 
Sciatica, 171, 181, 283. 
Sclera, 21 1. 
Scleritis, 211. 
Scotoma, 217. 

Scrotum, development of, 371. 
Secretin, 257, 270. 
Segmental innervation of upper 

limb, 155, 157. 
Semicircular canals, 206. 

ducts, 206. 
Semilunar (Gasserian) ganglion, 62. 
Semilunar ganglion. See Cceliac 

ganglion. 
Seminal vesicle, 377. 

28 



Sensory centres, higher, 12. 
fibres, course of, 44. 
decussation of, 43, 44. 
Septum, nasal, 325. 

pellucidum, 13. 
Sinus, cavernous, 1 15. 
relations of, 1 16. 
septic thrombosis of, 1 16. 
pocularis. See Prostatic utricle 
sagittal, inferior, 114. 

superior, 112. 
straight, 114. 

transverse (lateral), 23, 114, 207. 
venosus sclenv (canal of Schlemm), 
212. 
Skull, fracture of, 49, 109. 
Spastic paraplegia, 47. 
Speech centre, motor, 9. 

blood-supply of, 1 19. 
visual, 9. 
written, 8. 

blood-supply of, 1 1 9. 
Sphenoidal air sinus, 327. 
Spheno-palatine (Meckel's) gang- 
lion, 68. 
Spinal medulla, 40. 

compression of, 48. 
lesions of, 45. 
structure of, 43. 
Spino-thalamic tract, 44. 
Splanchnics, pelvic, of Gaskell, 285. 
Spleen, 403. 

contractions of, 406. 
enlargement of, 404. 
movable, 406. 
puncture of, 406. 
surface marking of, 404. 
venous congestion of, 274, 406. 
Splenectomy, 406. 
Stenosis, pulmonary, 307. 
Stereognosis, centre for, IO. 
Sternal angle, 294. 
Stomach, 242. 
atony of, 248. 
bed, 245. 
capacity of, 249. 
cardiac orifice of, 242. 
development of, 249. 
fundus of, 242, 247. 
lymph vessels of, 249. 
nerve-supply of, 249. 
pyloric canal of, 243. 



434 



INDEX 



Stomach, continued — 

radiographic examination of, 246. 

relations of, 243. 

secretion of, 24S. 

surface marking of, 243. 

viscero-motor reflex of, 250. 

viscero-sensory reflex of, 250. 
Stomata, 240, 346. 
Striae acoustics?, 89. 
Subcutaneous inguinal ring, 377. 
Subdural fluid, 109. 
Sublingual gland, 224. 
Submaxillary ganglion, 76. 

gland, 224. 
duct of, 224. 
Subphrenic abscess, intraperitoneal, 

258. 
Succus entericus, 257. 
Supra-renal gland, 407. 
Sympathetic ganglia, 186. 

nervous system, 185. 

cardiac branches of, 187. 
lesions of, 188. 
trunks, 185. 
Syndrome of Weber, 39. 
Syringo-myelia, 47. 

Tabes mesenterica, 256. 
Tarsal glands, 211. 
Tarsi, 210. 
Tartar, 225. 
Taste, centres for, 18. 
fibres, course of, 84. 
Teeth, 219. 

deciduous, 219. 
eruption of, 219. 
Hutchinson's, 220. 
lymph vessels of, 221. 
permanent, 219. 
Tegmen tympani, 200. 
Tegmentum, 18. 
Tela chorioidea, 15, 23. 
Tendons, division of, 122. 
Tentorium cerebelli, 109. 
Testis, 375. 

development of, 3S0. 
ducts of, 375. 
nerve-supply of, 375. 
Thalamus, 14, 29. 

lesions of, 30. 
Thoracic duct, 324. 

compression of, 321. 



Thoracic-ulnar analgesia, 160. 
Thumb, abduction of, 147. 

adduction of, 151. 
Thymus gland, 290, 412. 

tumours of, 413. 
Thyreo-glossal cyst, 411. 

duct, 411. 
Thyreoid cartilage, 330. 
gland. 409. 

blood-supply of, 412. 
development of, 411. 
lymph vessels of, 412. 
tumours of, 409. 
Thyreoidism, 41 1. 
Tic douloureux, 78. 
Tongue, 226. 

deviation of, 107. 
lymph vessels of, 226. 
muscles of, 107. 
nerve-supply of, 75, 107. 
paralysis of, 107. 
Tonsil, intestinal, 256. 
lingual, 226. 
palatine, 228. 
crypts of, 228. 
hypertrophy of, 228. 
lymph vessels of, 228. 
pharyngeal, 329. 
Tonsillitis, follicular, 228. 
Torticollis, 104. 
Torus tubarius, 329. 
Trachea, 339 

Tracheal tugging, 288, 321. 
Tractus solitarius, 85, 91. 
Transverse myelitis, 48. 
Traube's space, 244, 345. 
Trigeminal nerve, 61. 
compression of, 62. 
nuclear lesions of, 61. 
supranuclear lesions of, 61. 
neuralgia, 77. 
Tropical abscess of liver, 258, 317. 
Tubal pregnancy, 396. 
Tuber cinereum, 16. 
Tunica vaginalis testis, 375. 
Turbinated bones. See Conchae. 
Tympanic (mastoid) antrum, 1 14, 
202, 205. 
inflammation of, 206 
relations of, 205. 
membrane, 199, 202. 
Typhoid fever, 279. 



INDEX 



435 



Uncus, 16. 
Ureter, 361, 392. 
calculi in, 363. 
constrictions of, 362. 
development of, 369. 
nerve-supply of, 363. 
Ureteral colic, 363. 

muscular hyperalgesia in, 365. 
testicular pain in, 364. 
Urethra, 378. 

cavernous part of, 379. 
female, 399. 

membranous part of, 379. 
prostatic part of, 379. 
stricture of, 379. 
Urethral crest, 379. 
Urethro-vaginal fistula, 387. 
Urinary bladder, 365. 
Uterine tube, 390, 395. 
development of, 397. 
fimbria of, 395. 
ostium abdominale of, 396, 397. 
Utero-sacral ligament, 391. 
Uterus, 389. 

bicornuate, 398. 
blood-supply of, 392. 
body of, 390. 
broad ligament of, 385. 
development of, 397. 
displacement of, 391. 
ligaments of, 391. 
lymph vessels of, 393. 
nerve-supply of, 393. 
prolapse of, 389. 
Utricle, 207. 

Vagina, 387. 

development of, 397. 

lymph vessels of, 388. 

malignant disease of, 388. 
Vaginal examination, 387. 
Vagus nerve, 94. 
Valves, anal, 283. 

colic (ileo-crecal), 280. 

rectal, 282. 

venous, 301. 
Valvulse conniventes, 256. 
Varicocele, 375. 

Vas deferens. See Ductus deferens. 
Vein or Veins ; Vena or Vence — 

abdominal, superficial, 316. 

azygos (major), 351. 



Vein or Veins, continued — 
of brain, 121. 
cava inferior, 315. 

obstruction of, 316. 
superior, 314. 

obstruction of, 3 1 4. 
cerebral, great (of Galen), 27. 

internal, 27. 
hemorrhoidal, 275. 284. 
hepatic, 261, 317. 
innominate, 314. 
intercostal, 351. 
jugular, external, 302. 
internal, 301. 

thrombosis of, 200. 
meningeal, 117. 
mesenteric, superior, 272. 
ophthalmic, 1 15. 
pampiniform plexus, 375. 
para-umbilical, 275. 
portal, 271. 

obstruction of, 274. 
viscera drained by, 272. 
pterygoid plexus, 1 15. 
pulmonary, 317. 
splenic, 272, 406. 
umbilical, 260, 275, 304. 
Venous pulsation, 302, 311. 

ventricular type of, 312. 
Ventricle, fourth, 2, 1 5. 
lateral, 23. 
floor of, 23. 
inferior horn of, 27. 

tapping of, 27. 
medial wall of, 26. 
posterior horn of, 27. 
lapping of, 27. 
third, 15, 28. 
floor of, 16, 28. 
roof of, 29. 
Ventricular folds, 333. 
Vermiform process (appendix), 
277. 
development of, 278. 
nerve-supply of, 278. 
Vertebrae, erosion of, 321, 323. 
Vesical calculus, 373, 380. 

pain, 371. 
Vesico-vaginal fistula, 387. 
Viscera, nerve-supply of, 188. 
Visceral pain, 192. 
Viscero-motor reflex, 197. 



436 



INDEX 



Viscero-sensory reflex, 192. 
Visual centres, higher, 10, 12. 
blood-supply of, 120. 
lower, 31. 
fibres, lesions of, 32. 
Vitello-intestinal duct, 286. 
Vitreous body, 215. 
Vocal cords, false. See Ventricular 
folds, 
true. See Vocal folds. 
Vocal folds, 334. 

paralysis of, 320, 338. 

Weber's syndrome, 39. 
test, 90. 



Wernicke's test, 52. 

White rami communicantes, 

185. 
Winging of scapula, 133. 
Wolffian body, 380. 

duct, 369, 380. 
Word-deafness, 89. 
Word-hearing centre, 9. 

blood-supply of, 119. 
Word-seeing centre, 9. 

blood-supply of, 119. 
Wrist - drop paralysis, 140, 

141. 

Yolk-sac, 285. 



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